java.util

Class Collections


public class Collections
extends Object

This class consists exclusively of static methods that operate on or return collections. It contains polymorphic algorithms that operate on collections, "wrappers", which return a new collection backed by a specified collection, and a few other odds and ends.

The methods of this class all throw a NullPointerException if the collections or class objects provided to them are null.

The documentation for the polymorphic algorithms contained in this class generally includes a brief description of the implementation. Such descriptions should be regarded as implementation notes, rather than parts of the specification. Implementors should feel free to substitute other algorithms, so long as the specification itself is adhered to. (For example, the algorithm used by sort does not have to be a mergesort, but it does have to be stable.)

The "destructive" algorithms contained in this class, that is, the algorithms that modify the collection on which they operate, are specified to throw UnsupportedOperationException if the collection does not support the appropriate mutation primitive(s), such as the set method. These algorithms may, but are not required to, throw this exception if an invocation would have no effect on the collection. For example, invoking the sort method on an unmodifiable list that is already sorted may or may not throw UnsupportedOperationException.

This class is a member of the ../../../guide/collections/index.html"> Java Collections Framework.

Since:
1.2
See Also:
Collection, Set, List, Map

Field Summary

static List<E>
EMPTY_LIST
The empty list (immutable).
static Map<K,V>
EMPTY_MAP
The empty map (immutable).
static Set<E>
EMPTY_SET
The empty set (immutable).

Method Summary

static
ArrayList list(Enumeration e)
Returns an array list containing the elements returned by the specified enumeration in the order they are returned by the enumeration.
static
Collection checkedCollection(Collection c, Class type)
Returns a dynamically typesafe view of the specified collection.
static
Collection synchronizedCollection(Collection c)
Returns a synchronized (thread-safe) collection backed by the specified collection.
static
Collection unmodifiableCollection(T> c)
Returns an unmodifiable view of the specified collection.
static
Comparator reverseOrder()
Returns a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface.
static
Comparator reverseOrder(Comparator cmp)
Returns a comparator that imposes the reverse ordering of the specified comparator.
static
Enumeration enumeration(Collection c)
Returns an enumeration over the specified collection.
static
List checkedList(List list, Class type)
Returns a dynamically typesafe view of the specified list.
static
List emptyList()
Returns the empty list (immutable).
static
List nCopies(int n, T o)
Returns an immutable list consisting of n copies of the specified object.
static
List singletonList(T o)
Returns an immutable list containing only the specified object.
static
List synchronizedList(List list)
Returns a synchronized (thread-safe) list backed by the specified list.
static
List unmodifiableList(T> list)
Returns an unmodifiable view of the specified list.
static
Map emptyMap()
Returns the empty map (immutable).
static
Map singletonMap(K key, V value)
Returns an immutable map, mapping only the specified key to the specified value.
static
Map synchronizedMap(Map m)
Returns a synchronized (thread-safe) map backed by the specified map.
static
Map unmodifiableMap(extends K, V> m)
Returns an unmodifiable view of the specified map.
static
Set checkedSet(Set s, Class type)
Returns a dynamically typesafe view of the specified set.
static
Set emptySet()
Returns the empty set (immutable).
static
Set singleton(T o)
Returns an immutable set containing only the specified object.
static
Set synchronizedSet(Set s)
Returns a synchronized (thread-safe) set backed by the specified set.
static
Set unmodifiableSet(T> s)
Returns an unmodifiable view of the specified set.
static
SortedMap checkedSortedMap(SortedMap m, Class keyType, Class valueType)
Returns a dynamically typesafe view of the specified sorted map.
static
SortedMap synchronizedSortedMap(SortedMap m)
Returns a synchronized (thread-safe) sorted map backed by the specified sorted map.
static
SortedMap unmodifiableSortedMap(SortedMap m)
Returns an unmodifiable view of the specified sorted map.
static
SortedSet checkedSortedSet(SortedSet s, Class type)
Returns a dynamically typesafe view of the specified sorted set.
static
SortedSet synchronizedSortedSet(SortedSet s)
Returns a synchronized (thread-safe) sorted set backed by the specified sorted set.
static
SortedSet unmodifiableSortedSet(SortedSet s)
Returns an unmodifiable view of the specified sorted set.
static
T max(T> coll, T> comp)
Returns the maximum element of the given collection, according to the order induced by the specified comparator.
static
T min(T> coll, T> comp)
Returns the minimum element of the given collection, according to the order induced by the specified comparator.
static
V> Map checkedMap(Map m, Class keyType, Class valueType)
Returns a dynamically typesafe view of the specified map.
static
boolean addAll(T> c, T... a)
Adds all of the specified elements to the specified collection.
static
boolean replaceAll(List list, T oldVal, T newVal)
Replaces all occurrences of one specified value in a list with another.
static boolean
disjoint(Collection c1, Collection c2)
Returns true if the two specified collections have no elements in common.
static
extends Comparable> void sort(List list)
Sorts the specified list into ascending order, according to the natural ordering of its elements.
static
extends Object & Comparable> T max(T> coll)
Returns the maximum element of the given collection, according to the natural ordering of its elements.
static
extends Object & Comparable> T min(T> coll)
Returns the minimum element of the given collection, according to the natural ordering of its elements.
static int
frequency(Collection c, Object o)
Returns the number of elements in the specified collection equal to the specified object.
static int
indexOfSubList(List source, List target)
Returns the starting position of the first occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.
static
int binarySearch(T> list, T key, T> c)
Searches the specified list for the specified object using the binary search algorithm.
static
int binarySearch(T>> list, T key)
Searches the specified list for the specified object using the binary search algorithm.
static int
lastIndexOfSubList(List source, List target)
Returns the starting position of the last occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.
static void
reverse(List list)
Reverses the order of the elements in the specified list.
static void
rotate(List list, int distance)
Rotates the elements in the specified list by the specified distance.
static void
shuffle(List list)
Randomly permutes the specified list using a default source of randomness.
static void
shuffle(List list, Random rnd)
Randomly permute the specified list using the specified source of randomness.
static void
swap(List list, int i, int j)
Swaps the elements at the specified positions in the specified list.
static
void copy(T> dest, T> src)
Copies all of the elements from one list into another.
static
void fill(T> list, T obj)
Replaces all of the elements of the specified list with the specified element.
static
void sort(List list, T> c)
Sorts the specified list according to the order induced by the specified comparator.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

EMPTY_LIST

public static final List<E> EMPTY_LIST
The empty list (immutable). This list is serializable.
See Also:
emptyList()
Usages and Demos :

View More Examples of EMPTY_LIST
   1: import java.io.IOException;
   2: import java.util.Collections;
   3: 
   4:         ...
   5:       String[] classes= PackageUtils.findClassesInPackage("test.confordering",
   6:           Collections.EMPTY_LIST, Collections.EMPTY_LIST);
   7:       
   8:         ...
   9:       String[] classes= PackageUtils.findClassesInPackage("test.confordering.*",
  10:           Collections.EMPTY_LIST, Collections.EMPTY_LIST);
  11:       
  12:         ...
  13:       String[] classes= PackageUtils.findClassesInPackage("com.thoughtworks.qdox.parser",
  14:           Collections.EMPTY_LIST, Collections.EMPTY_LIST);

View Full Code Here
   1:                     + ")",
   2:                 Collections.singletonList(
   3:                     new java.sql.Date(expiryDate.getTime())));
   4:         ...
   5:                 "removeExpiredDiscountAsOf",
   6:                 Collections.singletonList(expiryDate));
   7: 
   8:         ...
   9:                 "suspendAllDiscounts",
  10:                 Collections.EMPTY_LIST);

View Full Code Here
   1:                 "findByName",
   2:                 Collections.singletonList(name));
   3: 
   4:         ...
   5:                 "findAllProducts",
   6:                 Collections.EMPTY_LIST);
   7: 
   8:         return new HashSet(
   9:             queryExecuter

View Full Code Here
   1:                 new byte[0],
   2:                 Collections.EMPTY_LIST,
   3:                 0,
   4:         ...
   5:                 new byte[] { 12 },
   6:                 Collections.singletonList(new byte[] { 12 }),
   7:                 0,
   8:         ...
   9:                 new byte[] { 12 },
  10:                 Collections.singletonList(singlePaddedRow),
  11:                 0,

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: 
   4:         ...
   5:                 ArrayUtils.EMPTY_BYTE_ARRAY, 404, "not found",
   6:                 Collections.EMPTY_LIST);
   7:         final WebResponse webResponse = new WebResponseImpl(webResponseData,
   8:                 URL_FIRST, SubmitMethod.GET, 10);
   9:         final FailingHttpStatusCodeException e = new FailingHttpStatusCodeException(

View Full Code Here

EMPTY_MAP

public static final Map<K,V> EMPTY_MAP
The empty map (immutable). This map is serializable.
Since:
1.3
See Also:
emptyMap()
Usages and Demos :

View More Examples of EMPTY_MAP
   1: 
   2: import java.util.Collections;
   3: import java.util.Map;
   4:         ...
   5:     protected Map load(Properties properties) throws Exception {
   6:         return Collections.EMPTY_MAP;
   7:     }
   8: 
   9:     public boolean loaded() {

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: import java.util.Set;
   4:         ...
   5:     public Set getClassAttributes () {
   6:         return Collections.EMPTY_SET;
   7:     }
   8:         ...
   9:     public Map getFieldAttributes () {
  10:         return Collections.EMPTY_MAP;
  11:     }
  12:         ...
  13:     public Map getMethodAttributes () {
  14:         return Collections.EMPTY_MAP;

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: import java.util.Map;
   4:         ...
   5:     public Map getImplementationHints() {
   6:         return Collections.EMPTY_MAP;
   7:     }
   8: }

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: import java.util.HashMap;
   4:         ...
   5:             if ( info == null ) {
   6:                 return Collections.EMPTY_MAP;
   7:             } else {
   8:                 return info;
   9:             }

View Full Code Here
   1: import java.util.Set;
   2: import java.util.Collections;
   3: import java.util.HashMap;
   4:         ...
   5:     public Set getPropertyNames() {
   6:         return Collections.EMPTY_SET;
   7:     }
   8:         ...
   9:     public Map getProperties() {
  10:         return Collections.EMPTY_MAP;
  11:     }

View Full Code Here

EMPTY_SET

public static final Set<E> EMPTY_SET
The empty set (immutable). This set is serializable.
See Also:
emptySet()
Usages and Demos :

View More Examples of EMPTY_SET
   1: 
   2: import java.util.Collections;
   3: import java.util.Set;
   4:         ...
   5:     public ModifiedFeatureIds(RevisionInfo fromRevision, RevisionInfo toRevision) {
   6:         this(fromRevision, toRevision, Collections.EMPTY_SET, Collections.EMPTY_SET,
   7:         ...
   8:                 Collections.EMPTY_SET);
   9:     }
  10:         ...
  11:     public Set getDeleted() {
  12:         return Collections.unmodifiableSet(deleted);

View Full Code Here
   1: import java.net.UnknownHostException;
   2: import java.util.Collections;
   3: import java.util.Set;
   4:         ...
   5:         super(RouterService.getMyGUID(),
   6:                 Collections.EMPTY_SET,
   7:                 0,
   8:                 UDPConnection.VERSION);
   9:     

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: import java.util.HashSet;
   4:         ...
   5:                                                                ins,
   6:                                                                Collections.EMPTY_SET,
   7:         ...
   8:                                                                Collections.EMPTY_SET,
   9:         ...
  10:                                                                Collections.EMPTY_SET,

View Full Code Here
   1: import java.util.Set;
   2: import java.util.Collections;
   3: 
   4:         ...
   5:       targets = ((target != null) ?
   6:          Collections.singleton( target ) :
   7:         ...
   8:          Collections.EMPTY_SET);
   9:     }

View Full Code Here
   1: import java.util.AbstractSet;
   2: import java.util.Collections;
   3: import java.util.HashMap;
   4:         ...
   5:             fireMapChange(Diffs.createMapDiff(addedKeys, removedKeys,
   6:                     Collections.EMPTY_SET, oldValues, newValues));
   7:         }
   8:     };

View Full Code Here

Method Details

ArrayList list

public static  ArrayList list(Enumeration e)
Returns an array list containing the elements returned by the specified enumeration in the order they are returned by the enumeration. This method provides interoperability between legacy APIs that return enumerations and new APIs that require collections.
Parameters:
e - enumeration providing elements for the returned array list
Returns:
an array list containing the elements returned by the specified enumeration.
Since:
1.4

Collection checkedCollection

public static  Collection checkedCollection(Collection c,
                                                  Class type)
Returns a dynamically typesafe view of the specified collection. Any attempt to insert an element of the wrong type will result in an immediate ClassCastException. Assuming a collection contains no incorrectly typed elements prior to the time a dynamically typesafe view is generated, and that all subsequent access to the collection takes place through the view, it is guaranteed that the collection cannot contain an incorrectly typed element.

The generics mechanism in the language provides compile-time (static) type checking, but it is possible to defeat this mechanism with unchecked casts. Usually this is not a problem, as the compiler issues warnings on all such unchecked operations. There are, however, times when static type checking alone is not sufficient. For example, suppose a collection is passed to a third-party library and it is imperative that the library code not corrupt the collection by inserting an element of the wrong type.

Another use of dynamically typesafe views is debugging. Suppose a program fails with a ClassCastException, indicating that an incorrectly typed element was put into a parameterized collection. Unfortunately, the exception can occur at any time after the erroneous element is inserted, so it typically provides little or no information as to the real source of the problem. If the problem is reproducible, one can quickly determine its source by temporarily modifying the program to wrap the collection with a dynamically typesafe view. For example, this declaration:

     Collection<String> c = new HashSet<String>();
 
may be replaced temporarily by this one:
     Collection<String> c = Collections.checkedCollection(
         new HashSet<String>(), String.class);
 
Running the program again will cause it to fail at the point where an incorrectly typed element is inserted into the collection, clearly identifying the source of the problem. Once the problem is fixed, the modified declaration may be reverted back to the original.

The returned collection does not pass the hashCode and equals operations through to the backing collection, but relies on Object's equals and hashCode methods. This is necessary to preserve the contracts of these operations in the case that the backing collection is a set or a list.

The returned collection will be serializable if the specified collection is serializable.

Parameters:
c - the collection for which a dynamically typesafe view is to be returned
type - the type of element that c is permitted to hold
Returns:
a dynamically typesafe view of the specified collection
Since:
1.5

Collection synchronizedCollection

public static  Collection synchronizedCollection(Collection c)
Returns a synchronized (thread-safe) collection backed by the specified collection. In order to guarantee serial access, it is critical that all access to the backing collection is accomplished through the returned collection.

It is imperative that the user manually synchronize on the returned collection when iterating over it:

  Collection c = Collections.synchronizedCollection(myCollection);
     ...
  synchronized(c) {
      Iterator i = c.iterator(); // Must be in the synchronized block
      while (i.hasNext())
         foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned collection does not pass the hashCode and equals operations through to the backing collection, but relies on Object's equals and hashCode methods. This is necessary to preserve the contracts of these operations in the case that the backing collection is a set or a list.

The returned collection will be serializable if the specified collection is serializable.

Parameters:
c - the collection to be "wrapped" in a synchronized collection.
Returns:
a synchronized view of the specified collection.

Collection unmodifiableCollection

public static  Collection unmodifiableCollection(T> c)
Returns an unmodifiable view of the specified collection. This method allows modules to provide users with "read-only" access to internal collections. Query operations on the returned collection "read through" to the specified collection, and attempts to modify the returned collection, whether direct or via its iterator, result in an UnsupportedOperationException.

The returned collection does not pass the hashCode and equals operations through to the backing collection, but relies on Object's equals and hashCode methods. This is necessary to preserve the contracts of these operations in the case that the backing collection is a set or a list.

The returned collection will be serializable if the specified collection is serializable.

Parameters:
c - the collection for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified collection.

Comparator reverseOrder

public static  Comparator reverseOrder()
Returns a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface. (The natural ordering is the ordering imposed by the objects' own compareTo method.) This enables a simple idiom for sorting (or maintaining) collections (or arrays) of objects that implement the Comparable interface in reverse-natural-order. For example, suppose a is an array of strings. Then:
 		Arrays.sort(a, Collections.reverseOrder());
 
sorts the array in reverse-lexicographic (alphabetical) order.

The returned comparator is serializable.

Returns:
a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface.
See Also:
Comparable

Comparator reverseOrder

public static  Comparator reverseOrder(Comparator cmp)
Returns a comparator that imposes the reverse ordering of the specified comparator. If the specified comparator is null, this method is equivalent to reverseOrder() (in other words, it returns a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface).

The returned comparator is serializable (assuming the specified comparator is also serializable or null).

Returns:
a comparator that imposes the reverse ordering of the specified comparator.
Since:
1.5

Enumeration enumeration

public static  Enumeration enumeration(Collection c)
Returns an enumeration over the specified collection. This provides interoperability with legacy APIs that require an enumeration as input.
Parameters:
c - the collection for which an enumeration is to be returned.
Returns:
an enumeration over the specified collection.
See Also:
Enumeration

List checkedList

public static  List checkedList(List list,
                                      Class type)
Returns a dynamically typesafe view of the specified list. Any attempt to insert an element of the wrong type will result in an immediate ClassCastException. Assuming a list contains no incorrectly typed elements prior to the time a dynamically typesafe view is generated, and that all subsequent access to the list takes place through the view, it is guaranteed that the list cannot contain an incorrectly typed element.

A discussion of the use of dynamically typesafe views may be found in the documentation for the checkedCollection method.

The returned list will be serializable if the specified list is serializable.

Parameters:
list - the list for which a dynamically typesafe view is to be returned
type - the type of element that list is permitted to hold
Returns:
a dynamically typesafe view of the specified list
Since:
1.5

List emptyList

public static final  List emptyList()
Returns the empty list (immutable). This list is serializable.

This example illustrates the type-safe way to obtain an empty list:

     List<String> s = Collections.emptyList();
 
Implementation note: Implementations of this method need not create a separate List object for each call. Using this method is likely to have comparable cost to using the like-named field. (Unlike this method, the field does not provide type safety.)
Since:
1.5
See Also:
EMPTY_LIST

List nCopies

public static  List nCopies(int n,
                                  T o)
Returns an immutable list consisting of n copies of the specified object. The newly allocated data object is tiny (it contains a single reference to the data object). This method is useful in combination with the List.addAll method to grow lists. The returned list is serializable.
Parameters:
n - the number of elements in the returned list.
o - the element to appear repeatedly in the returned list.
Returns:
an immutable list consisting of n copies of the specified object.
Throws:
IllegalArgumentException - if n < 0.
See Also:
List.addAll(Collection), List.addAll(int, Collection)

List singletonList

public static  List singletonList(T o)
Returns an immutable list containing only the specified object. The returned list is serializable.
Parameters:
o - the sole object to be stored in the returned list.
Returns:
an immutable list containing only the specified object.
Since:
1.3

List synchronizedList

public static  List synchronizedList(List list)
Returns a synchronized (thread-safe) list backed by the specified list. In order to guarantee serial access, it is critical that all access to the backing list is accomplished through the returned list.

It is imperative that the user manually synchronize on the returned list when iterating over it:

  List list = Collections.synchronizedList(new ArrayList());
      ...
  synchronized(list) {
      Iterator i = list.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned list will be serializable if the specified list is serializable.

Parameters:
list - the list to be "wrapped" in a synchronized list.
Returns:
a synchronized view of the specified list.

List unmodifiableList

public static  List unmodifiableList(T> list)
Returns an unmodifiable view of the specified list. This method allows modules to provide users with "read-only" access to internal lists. Query operations on the returned list "read through" to the specified list, and attempts to modify the returned list, whether direct or via its iterator, result in an UnsupportedOperationException.

The returned list will be serializable if the specified list is serializable. Similarly, the returned list will implement RandomAccess if the specified list does.

Parameters:
list - the list for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified list.

Map emptyMap

public static final  Map emptyMap()
Returns the empty map (immutable). This map is serializable.

This example illustrates the type-safe way to obtain an empty set:

     Map<String, Date> s = Collections.emptyMap();
 
Implementation note: Implementations of this method need not create a separate Map object for each call. Using this method is likely to have comparable cost to using the like-named field. (Unlike this method, the field does not provide type safety.)
Since:
1.5
See Also:
EMPTY_MAP

Map singletonMap

public static  Map singletonMap(K key,
                                          V value)
Returns an immutable map, mapping only the specified key to the specified value. The returned map is serializable.
Parameters:
key - the sole key to be stored in the returned map.
value - the value to which the returned map maps key.
Returns:
an immutable map containing only the specified key-value mapping.
Since:
1.3

Map synchronizedMap

public static  Map synchronizedMap(Map m)
Returns a synchronized (thread-safe) map backed by the specified map. In order to guarantee serial access, it is critical that all access to the backing map is accomplished through the returned map.

It is imperative that the user manually synchronize on the returned map when iterating over any of its collection views:

  Map m = Collections.synchronizedMap(new HashMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized(m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned map will be serializable if the specified map is serializable.

Parameters:
m - the map to be "wrapped" in a synchronized map.
Returns:
a synchronized view of the specified map.

Map unmodifiableMap

public static  Map unmodifiableMap(extends K,
                                             V> m)
Returns an unmodifiable view of the specified map. This method allows modules to provide users with "read-only" access to internal maps. Query operations on the returned map "read through" to the specified map, and attempts to modify the returned map, whether direct or via its collection views, result in an UnsupportedOperationException.

The returned map will be serializable if the specified map is serializable.

Parameters:
m - the map for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified map.

Set checkedSet

public static  Set checkedSet(Set s,
                                    Class type)
Returns a dynamically typesafe view of the specified set. Any attempt to insert an element of the wrong type will result in an immediate ClassCastException. Assuming a set contains no incorrectly typed elements prior to the time a dynamically typesafe view is generated, and that all subsequent access to the set takes place through the view, it is guaranteed that the set cannot contain an incorrectly typed element.

A discussion of the use of dynamically typesafe views may be found in the documentation for the checkedCollection method.

The returned set will be serializable if the specified set is serializable.

Parameters:
s - the set for which a dynamically typesafe view is to be returned
type - the type of element that s is permitted to hold
Returns:
a dynamically typesafe view of the specified set
Since:
1.5

Set emptySet

public static final  Set emptySet()
Returns the empty set (immutable). This set is serializable. Unlike the like-named field, this method is parameterized.

This example illustrates the type-safe way to obtain an empty set:

     Set<String> s = Collections.emptySet();
 
Implementation note: Implementations of this method need not create a separate Set object for each call. Using this method is likely to have comparable cost to using the like-named field. (Unlike this method, the field does not provide type safety.)
Since:
1.5
See Also:
EMPTY_SET

Set singleton

public static  Set singleton(T o)
Returns an immutable set containing only the specified object. The returned set is serializable.
Parameters:
o - the sole object to be stored in the returned set.
Returns:
an immutable set containing only the specified object.

Set synchronizedSet

public static  Set synchronizedSet(Set s)
Returns a synchronized (thread-safe) set backed by the specified set. In order to guarantee serial access, it is critical that all access to the backing set is accomplished through the returned set.

It is imperative that the user manually synchronize on the returned set when iterating over it:

  Set s = Collections.synchronizedSet(new HashSet());
      ...
  synchronized(s) {
      Iterator i = s.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned set will be serializable if the specified set is serializable.

Parameters:
s - the set to be "wrapped" in a synchronized set.
Returns:
a synchronized view of the specified set.

Set unmodifiableSet

public static  Set unmodifiableSet(T> s)
Returns an unmodifiable view of the specified set. This method allows modules to provide users with "read-only" access to internal sets. Query operations on the returned set "read through" to the specified set, and attempts to modify the returned set, whether direct or via its iterator, result in an UnsupportedOperationException.

The returned set will be serializable if the specified set is serializable.

Parameters:
s - the set for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified set.

SortedMap checkedSortedMap

public static  SortedMap checkedSortedMap(SortedMap m,
                                                    Class keyType,
                                                    Class valueType)
Returns a dynamically typesafe view of the specified sorted map. Any attempt to insert a mapping whose key or value have the wrong type will result in an immediate ClassCastException. Similarly, any attempt to modify the value currently associated with a key will result in an immediate ClassCastException, whether the modification is attempted directly through the map itself, or through a Map.Entry instance obtained from the map's entry set view.

Assuming a map contains no incorrectly typed keys or values prior to the time a dynamically typesafe view is generated, and that all subsequent access to the map takes place through the view (or one of its collection views), it is guaranteed that the map cannot contain an incorrectly typed key or value.

A discussion of the use of dynamically typesafe views may be found in the documentation for the checkedCollection method.

The returned map will be serializable if the specified map is serializable.

Parameters:
m - the map for which a dynamically typesafe view is to be returned
keyType - the type of key that m is permitted to hold
valueType - the type of value that m is permitted to hold
Returns:
a dynamically typesafe view of the specified map
Since:
1.5

SortedMap synchronizedSortedMap

public static  SortedMap synchronizedSortedMap(SortedMap m)
Returns a synchronized (thread-safe) sorted map backed by the specified sorted map. In order to guarantee serial access, it is critical that all access to the backing sorted map is accomplished through the returned sorted map (or its views).

It is imperative that the user manually synchronize on the returned sorted map when iterating over any of its collection views, or the collections views of any of its subMap, headMap or tailMap views.

  SortedMap m = Collections.synchronizedSortedMap(new HashSortedMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized(m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
or:
  SortedMap m = Collections.synchronizedSortedMap(new HashSortedMap());
  SortedMap m2 = m.subMap(foo, bar);
      ...
  Set s2 = m2.keySet();  // Needn't be in synchronized block
      ...
  synchronized(m) {  // Synchronizing on m, not m2 or s2!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned sorted map will be serializable if the specified sorted map is serializable.

Parameters:
m - the sorted map to be "wrapped" in a synchronized sorted map.
Returns:
a synchronized view of the specified sorted map.

SortedMap unmodifiableSortedMap

public static  SortedMap unmodifiableSortedMap(SortedMap m)
Returns an unmodifiable view of the specified sorted map. This method allows modules to provide users with "read-only" access to internal sorted maps. Query operations on the returned sorted map "read through" to the specified sorted map. Attempts to modify the returned sorted map, whether direct, via its collection views, or via its subMap, headMap, or tailMap views, result in an UnsupportedOperationException.

The returned sorted map will be serializable if the specified sorted map is serializable.

Parameters:
m - the sorted map for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified sorted map.

SortedSet checkedSortedSet

public static  SortedSet checkedSortedSet(SortedSet s,
                                                Class type)
Returns a dynamically typesafe view of the specified sorted set. Any attempt to insert an element of the wrong type will result in an immediate ClassCastException. Assuming a sorted set contains no incorrectly typed elements prior to the time a dynamically typesafe view is generated, and that all subsequent access to the sorted set takes place through the view, it is guaranteed that the sorted set cannot contain an incorrectly typed element.

A discussion of the use of dynamically typesafe views may be found in the documentation for the checkedCollection method.

The returned sorted set will be serializable if the specified sorted set is serializable.

Parameters:
s - the sorted set for which a dynamically typesafe view is to be returned
type - the type of element that s is permitted to hold
Returns:
a dynamically typesafe view of the specified sorted set
Since:
1.5

SortedSet synchronizedSortedSet

public static  SortedSet synchronizedSortedSet(SortedSet s)
Returns a synchronized (thread-safe) sorted set backed by the specified sorted set. In order to guarantee serial access, it is critical that all access to the backing sorted set is accomplished through the returned sorted set (or its views).

It is imperative that the user manually synchronize on the returned sorted set when iterating over it or any of its subSet, headSet, or tailSet views.

  SortedSet s = Collections.synchronizedSortedSet(new HashSortedSet());
      ...
  synchronized(s) {
      Iterator i = s.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
or:
  SortedSet s = Collections.synchronizedSortedSet(new HashSortedSet());
  SortedSet s2 = s.headSet(foo);
      ...
  synchronized(s) {  // Note: s, not s2!!!
      Iterator i = s2.iterator(); // Must be in the synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned sorted set will be serializable if the specified sorted set is serializable.

Parameters:
s - the sorted set to be "wrapped" in a synchronized sorted set.
Returns:
a synchronized view of the specified sorted set.

SortedSet unmodifiableSortedSet

public static  SortedSet unmodifiableSortedSet(SortedSet s)
Returns an unmodifiable view of the specified sorted set. This method allows modules to provide users with "read-only" access to internal sorted sets. Query operations on the returned sorted set "read through" to the specified sorted set. Attempts to modify the returned sorted set, whether direct, via its iterator, or via its subSet, headSet, or tailSet views, result in an UnsupportedOperationException.

The returned sorted set will be serializable if the specified sorted set is serializable.

Parameters:
s - the sorted set for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified sorted set.

T max

public static  T max(T> coll,
                        T> comp)
Returns the maximum element of the given collection, according to the order induced by the specified comparator. All elements in the collection must be mutually comparable by the specified comparator (that is, comp.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the collection).

This method iterates over the entire collection, hence it requires time proportional to the size of the collection.

Parameters:
coll - the collection whose maximum element is to be determined.
comp - the comparator with which to determine the maximum element. A null value indicates that the elements' natural ordering should be used.
Returns:
the maximum element of the given collection, according to the specified comparator.
Throws:
ClassCastException - if the collection contains elements that are not mutually comparable using the specified comparator.
NoSuchElementException - if the collection is empty.
See Also:
Comparable

T min

public static  T min(T> coll,
                        T> comp)
Returns the minimum element of the given collection, according to the order induced by the specified comparator. All elements in the collection must be mutually comparable by the specified comparator (that is, comp.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the collection).

This method iterates over the entire collection, hence it requires time proportional to the size of the collection.

Parameters:
coll - the collection whose minimum element is to be determined.
comp - the comparator with which to determine the minimum element. A null value indicates that the elements' natural ordering should be used.
Returns:
the minimum element of the given collection, according to the specified comparator.
Throws:
ClassCastException - if the collection contains elements that are not mutually comparable using the specified comparator.
NoSuchElementException - if the collection is empty.
See Also:
Comparable

V> Map checkedMap

public static V> Map checkedMap(Map m,
                                          Class keyType,
                                          Class valueType)
Returns a dynamically typesafe view of the specified map. Any attempt to insert a mapping whose key or value have the wrong type will result in an immediate ClassCastException. Similarly, any attempt to modify the value currently associated with a key will result in an immediate ClassCastException, whether the modification is attempted directly through the map itself, or through a Map.Entry instance obtained from the map's entry set view.

Assuming a map contains no incorrectly typed keys or values prior to the time a dynamically typesafe view is generated, and that all subsequent access to the map takes place through the view (or one of its collection views), it is guaranteed that the map cannot contain an incorrectly typed key or value.

A discussion of the use of dynamically typesafe views may be found in the documentation for the checkedCollection method.

The returned map will be serializable if the specified map is serializable.

Parameters:
m - the map for which a dynamically typesafe view is to be returned
keyType - the type of key that m is permitted to hold
valueType - the type of value that m is permitted to hold
Returns:
a dynamically typesafe view of the specified map
Since:
1.5

boolean addAll

public static  boolean addAll(T> c,
                                 T... a)
Adds all of the specified elements to the specified collection. Elements to be added may be specified individually or as an array. The behavior of this convenience method is identical to that of c.addAll(Arrays.asList(elements)), but this method is likely to run significantly faster under most implementations.

When elements are specified individually, this method provides a convenient way to add a few elements to an existing collection:

     Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
 
Parameters:
c - the collection into which elements are to be inserted
a - the elements to insert into c
Returns:
true if the collection changed as a result of the call
Throws:
UnsupportedOperationException - if c does not support the add method
NullPointerException - if elements contains one or more null values and c does not support null elements, or if c or elements are null
IllegalArgumentException - if some aspect of a value in elements prevents it from being added to c
Since:
1.5
See Also:
Collection.addAll(Collection)

boolean replaceAll

public static  boolean replaceAll(List list,
                                     T oldVal,
                                     T newVal)
Replaces all occurrences of one specified value in a list with another. More formally, replaces with newVal each element e in list such that (oldVal==null ? e==null : oldVal.equals(e)). (This method has no effect on the size of the list.)
Parameters:
list - the list in which replacement is to occur.
oldVal - the old value to be replaced.
newVal - the new value with which oldVal is to be replaced.
Returns:
true if list contained one or more elements e such that (oldVal==null ? e==null : oldVal.equals(e)).
Throws:
UnsupportedOperationException - if the specified list or its list-iterator does not support the set method.
Since:
1.4

disjoint

public static boolean disjoint(Collection c1,
                               Collection c2)
Returns true if the two specified collections have no elements in common.

Care must be exercised if this method is used on collections that do not comply with the general contract for Collection. Implementations may elect to iterate over either collection and test for containment in the other collection (or to perform any equivalent computation). If either collection uses a nonstandard equality test (as does a SortedSet whose ordering is not compatible with equals, or the key set of an IdentityHashMap), both collections must use the same nonstandard equality test, or the result of this method is undefined.

Note that it is permissible to pass the same collection in both parameters, in which case the method will return true if and only if the collection is empty.

Parameters:
c1 - a collection
c2 - a collection
Throws:
NullPointerException - if either collection is null
Since:
1.5
Usages and Demos :

View More Examples of disjoint(Collection c1,Collection c2)
   1:     print("'list' disjoint (Four)?: " +
   2:       Collections.disjoint(list,
   3:         ...
   4:         Collections.singletonList("Four")));
   5:         ...
   6:     print("max: " + Collections.max(list));
   7:     print("min: " + Collections.min(list));
   8:         ...
   9:     print("'list' disjoint 'dups'?: " +
  10:       Collections.disjoint(list, dups));

View Full Code Here

extends Comparable> void sort

public static extends Comparable> void sort(List list)
Sorts the specified list into ascending order, according to the natural ordering of its elements. All elements in the list must implement the Comparable interface. Furthermore, all elements in the list must be mutually comparable (that is, e1.compareTo(e2) must not throw a ClassCastException for any elements e1 and e2 in the list).

This sort is guaranteed to be stable: equal elements will not be reordered as a result of the sort.

The specified list must be modifiable, but need not be resizable.

The sorting algorithm is a modified mergesort (in which the merge is omitted if the highest element in the low sublist is less than the lowest element in the high sublist). This algorithm offers guaranteed n log(n) performance. This implementation dumps the specified list into an array, sorts the array, and iterates over the list resetting each element from the corresponding position in the array. This avoids the n2 log(n) performance that would result from attempting to sort a linked list in place.

Parameters:
list - the list to be sorted.
Throws:
ClassCastException - if the list contains elements that are not mutually comparable (for example, strings and integers).
UnsupportedOperationException - if the specified list's list-iterator does not support the set operation.
See Also:
Comparable

extends Object & Comparable> T max

public static extends Object & Comparable> T max(T> coll)
Returns the maximum element of the given collection, according to the natural ordering of its elements. All elements in the collection must implement the Comparable interface. Furthermore, all elements in the collection must be mutually comparable (that is, e1.compareTo(e2) must not throw a ClassCastException for any elements e1 and e2 in the collection).

This method iterates over the entire collection, hence it requires time proportional to the size of the collection.

Parameters:
coll - the collection whose maximum element is to be determined.
Returns:
the maximum element of the given collection, according to the natural ordering of its elements.
Throws:
ClassCastException - if the collection contains elements that are not mutually comparable (for example, strings and integers).
NoSuchElementException - if the collection is empty.
See Also:
Comparable

extends Object & Comparable> T min

public static extends Object & Comparable> T min(T> coll)
Returns the minimum element of the given collection, according to the natural ordering of its elements. All elements in the collection must implement the Comparable interface. Furthermore, all elements in the collection must be mutually comparable (that is, e1.compareTo(e2) must not throw a ClassCastException for any elements e1 and e2 in the collection).

This method iterates over the entire collection, hence it requires time proportional to the size of the collection.

Parameters:
coll - the collection whose minimum element is to be determined.
Returns:
the minimum element of the given collection, according to the natural ordering of its elements.
Throws:
ClassCastException - if the collection contains elements that are not mutually comparable (for example, strings and integers).
NoSuchElementException - if the collection is empty.
See Also:
Comparable

frequency

public static int frequency(Collection c,
                            Object o)
Returns the number of elements in the specified collection equal to the specified object. More formally, returns the number of elements e in the collection such that (o == null ? e == null : o.equals(e)).
Parameters:
c - the collection in which to determine the frequency of o
o - the object whose frequency is to be determined
Throws:
NullPointerException - if c is null
Since:
1.5
Usages and Demos :

View More Examples of frequency(Collection c,Object o)
   1:     print("'list' disjoint (Four)?: " +
   2:       Collections.disjoint(list,
   3:         ...
   4:         Collections.singletonList("Four")));
   5:         ...
   6:     print("max: " + Collections.max(list));
   7:     print("min: " + Collections.min(list));
   8:         ...
   9:     print("frequency of 'pop': " +
  10:       Collections.frequency(list, "pop"));

View Full Code Here

indexOfSubList

public static int indexOfSubList(List source,
                                 List target)
Returns the starting position of the first occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence. More formally, returns the lowest index i such that source.subList(i, i+target.size()).equals(target), or -1 if there is no such index. (Returns -1 if target.size() > source.size().)

This implementation uses the "brute force" technique of scanning over the source list, looking for a match with the target at each location in turn.

Parameters:
source - the list in which to search for the first occurrence of target.
target - the list to search for as a subList of source.
Returns:
the starting position of the first occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.
Since:
1.4
Usages and Demos :

View More Examples of indexOfSubList(List source,List target)
   1:     print("'list' disjoint (Four)?: " +
   2:       Collections.disjoint(list,
   3:         ...
   4:         Collections.singletonList("Four")));
   5:         ...
   6:     print("max: " + Collections.max(list));
   7:     print("min: " + Collections.min(list));
   8:         ...
   9:     print("indexOfSubList: " +
  10:       Collections.indexOfSubList(list, sublist));

View Full Code Here
   1: 
   2: public class Collections {
   3: 
   4:         ...
   5:     private Collections() {}
   6: 
   7:         ...
   8:     public static void sort(List list) {
   9:         java.util.Collections.sort(list);
  10:     }
  11:         ...
  12:     public static int indexOfSubList(List source, List target) {
  13:         return java.util.Collections.indexOfSubList(source, target);

View Full Code Here

int binarySearch

public static  int binarySearch(T> list,
                                   T key,
                                   T> c)
Searches the specified list for the specified object using the binary search algorithm. The list must be sorted into ascending order according to the specified comparator (as by the Sort(List, Comparator) method, above), prior to making this call. If it is not sorted, the results are undefined. If the list contains multiple elements equal to the specified object, there is no guarantee which one will be found.

This method runs in log(n) time for a "random access" list (which provides near-constant-time positional access). If the specified list does not implement the RandomAccess interface and is large, this method will do an iterator-based binary search that performs O(n) link traversals and O(log n) element comparisons.

Parameters:
list - the list to be searched.
key - the key to be searched for.
c - the comparator by which the list is ordered. A null value indicates that the elements' natural ordering should be used.
Returns:
index of the search key, if it is contained in the list; otherwise, (-(insertion point) - 1). The insertion point is defined as the point at which the key would be inserted into the list: the index of the first element greater than the key, or list.size(), if all elements in the list are less than the specified key. Note that this guarantees that the return value will be >= 0 if and only if the key is found.
Throws:
ClassCastException - if the list contains elements that are not mutually comparable using the specified comparator, or the search key in not mutually comparable with the elements of the list using this comparator.
See Also:
Comparable, sort(List, Comparator)

int binarySearch

public static  int binarySearch(T>> list,
                                   T key)
Searches the specified list for the specified object using the binary search algorithm. The list must be sorted into ascending order according to the natural ordering of its elements (as by the sort(List) method, above) prior to making this call. If it is not sorted, the results are undefined. If the list contains multiple elements equal to the specified object, there is no guarantee which one will be found.

This method runs in log(n) time for a "random access" list (which provides near-constant-time positional access). If the specified list does not implement the RandomAccess interface and is large, this method will do an iterator-based binary search that performs O(n) link traversals and O(log n) element comparisons.

Parameters:
list - the list to be searched.
key - the key to be searched for.
Returns:
index of the search key, if it is contained in the list; otherwise, (-(insertion point) - 1). The insertion point is defined as the point at which the key would be inserted into the list: the index of the first element greater than the key, or list.size(), if all elements in the list are less than the specified key. Note that this guarantees that the return value will be >= 0 if and only if the key is found.
Throws:
ClassCastException - if the list contains elements that are not mutually comparable (for example, strings and integers), or the search key in not mutually comparable with the elements of the list.
See Also:
Comparable, sort(List)

lastIndexOfSubList

public static int lastIndexOfSubList(List source,
                                     List target)
Returns the starting position of the last occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence. More formally, returns the highest index i such that source.subList(i, i+target.size()).equals(target), or -1 if there is no such index. (Returns -1 if target.size() > source.size().)

This implementation uses the "brute force" technique of iterating over the source list, looking for a match with the target at each location in turn.

Parameters:
source - the list in which to search for the last occurrence of target.
target - the list to search for as a subList of source.
Returns:
the starting position of the last occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.
Since:
1.4
Usages and Demos :

View More Examples of lastIndexOfSubList(List source,List target)
   1:     print("'list' disjoint (Four)?: " +
   2:       Collections.disjoint(list,
   3:         ...
   4:         Collections.singletonList("Four")));
   5:         ...
   6:     print("max: " + Collections.max(list));
   7:     print("min: " + Collections.min(list));
   8:         ...
   9:     print("lastIndexOfSubList: " +
  10:       Collections.lastIndexOfSubList(list, sublist));

View Full Code Here
   1:         ascending = newAscending;
   2:         Collections.sort(data, getComparator());        
   3:     }
   4:         ...
   5:     private int getInsertionPoint(ModelItem item) {
   6:         int position = Collections.binarySearch(data, item, getComparator());
   7:         if (position < 0) {
   8:         ...
   9:         } else {
  10:             position = Collections.lastIndexOfSubList(data, Collections.singletonList(data.get(position)));
  11:             position++;

View Full Code Here
   1: 
   2: public class Collections {
   3: 
   4:         ...
   5:     private Collections() {}
   6: 
   7:         ...
   8:     public static void sort(List list) {
   9:         java.util.Collections.sort(list);
  10:     }
  11:         ...
  12:     public static int lastIndexOfSubList(List source, List target) {
  13:         return java.util.Collections.lastIndexOfSubList(source, target);

View Full Code Here

reverse

public static void reverse(List list)
Reverses the order of the elements in the specified list.

This method runs in linear time.

Parameters:
list - the list whose elements are to be reversed.
Throws:
UnsupportedOperationException - if the specified list or its list-iterator does not support the set method.
Usages and Demos :

View More Examples of reverse(List list)
   1:         } else if (arg instanceof List){
   2:             Collections.reverse((List)arg);
   3:         } else if (arg instanceof Map){
   4:             return reverseMap((Map)arg);
   5:         } else if (arg instanceof String){

View Full Code Here
   1: import java.util.Collection;
   2: import java.util.Collections;
   3: import java.util.HashMap;
   4:         ...
   5:             
   6:             Collections.sort(bestMatches);
   7:         ...
   8:             Collections.reverse(bestMatches);
   9:             throw new NotEnoughContiguousSeatsException(this.classId, howMany, bestMatches);

View Full Code Here
   1: import java.lang.ref.WeakReference;
   2: import java.util.Collections;
   3: import java.util.List;
   4:         ...
   5:         List<Class> appClasses = ac.getApplicationClasses(appClass);
   6:         Collections.reverse(appClasses);
   7:         ApplicationActionMap parent = null;
   8:         for(Class cls : appClasses) {
   9:         parent = createApplicationActionMap(appClass, cls, appObject, parent);

View Full Code Here
   1: 
   2:         private List<TreeNode> children = Collections.emptyList();
   3: 
   4:         ...
   5:             minSize = Math.min(chain.size(), minSize);
   6:             Collections.reverse(chain);
   7:             chains.add(chain);
   8:         }

View Full Code Here
   1: import java.util.Collection;
   2: import java.util.Collections;
   3: import java.util.List;
   4:         ...
   5:                     CellOperation.VIEW);
   6:             Collections.reverse(children);
   7:             for (Cell childCell : children) {
   8:                 WebObject child = childCell.getWebObject();
   9:                 if (childCell.getResultState() == ResultState.PUBLISHED

View Full Code Here

rotate

public static void rotate(List list,
                          int distance)
Rotates the elements in the specified list by the specified distance. After calling this method, the element at index i will be the element previously at index (i - distance) mod list.size(), for all values of i between 0 and list.size()-1, inclusive. (This method has no effect on the size of the list.)

For example, suppose list comprises [t, a, n, k, s]. After invoking Collections.rotate(list, 1) (or Collections.rotate(list, -4)), list will comprise [s, t, a, n, k].

Note that this method can usefully be applied to sublists to move one or more elements within a list while preserving the order of the remaining elements. For example, the following idiom moves the element at index j forward to position k (which must be greater than or equal to j):

     Collections.rotate(list.subList(j, k+1), -1);
 
To make this concrete, suppose list comprises [a, b, c, d, e]. To move the element at index 1 (b) forward two positions, perform the following invocation:
     Collections.rotate(l.subList(1, 4), -1);
 
The resulting list is [a, c, d, b, e].

To move more than one element forward, increase the absolute value of the rotation distance. To move elements backward, use a positive shift distance.

If the specified list is small or implements the RandomAccess interface, this implementation exchanges the first element into the location it should go, and then repeatedly exchanges the displaced element into the location it should go until a displaced element is swapped into the first element. If necessary, the process is repeated on the second and successive elements, until the rotation is complete. If the specified list is large and doesn't implement the RandomAccess interface, this implementation breaks the list into two sublist views around index -distance mod size. Then the reverse(List) method is invoked on each sublist view, and finally it is invoked on the entire list. For a more complete description of both algorithms, see Section 2.3 of Jon Bentley's Programming Pearls (Addison-Wesley, 1986).

Parameters:
list - the list to be rotated.
distance - the distance to rotate the list. There are no constraints on this value; it may be zero, negative, or greater than list.size().
Throws:
UnsupportedOperationException - if the specified list or its list-iterator does not support the set method.
Since:
1.4
Usages and Demos :

View More Examples of rotate(List list,int distance)
   1:     print("'list' disjoint (Four)?: " +
   2:       Collections.disjoint(list,
   3:         ...
   4:         Collections.singletonList("Four")));
   5:         ...
   6:     print("max: " + Collections.max(list));
   7:     print("min: " + Collections.min(list));
   8:         ...
   9:     print("reverse: " + list);
  10:     Collections.rotate(list, 3);

View Full Code Here
   1:     protected void coupe(int n){
   2:         Collections.rotate(d,n);
   3:         informPlayers(Player.INFORM_COUPE,Math.min(29,Math.max(3,(n + (int) Math.round(4 - Math.random() * 5)))),p[cP]);
   4:         ...
   5:         for(int i = 0;i<4;i++){
   6:             Collections.sort(p[i].getHand());
   7:             p[i].setAnnonces(Ruler.getAnnonces (p[i].getHand(),Annonce.TOUT_AT,0));
   8:         }
   9:         informPlayers(Player.INFORM_DISTRIBUTE,n,p[cP]);

View Full Code Here
   1: 
   2: public class Collections {
   3: 
   4:         ...
   5:     private Collections() {}
   6: 
   7:         ...
   8:     public static void sort(List list) {
   9:         java.util.Collections.sort(list);
  10:     }
  11:         ...
  12:     public static void rotate(List list, int distance) {
  13:         java.util.Collections.rotate(list, distance);

View Full Code Here
   1: import java.util.Collection;
   2: import java.util.Collections;
   3: import java.util.Iterator;
   4:         ...
   5:   {
   6:     XList list = createXList(Collections.EMPTY_LIST);
   7:     ArrayList verifyList = new ArrayList();
   8:         ...
   9:   {
  10:     XList list = createXList(Collections.EMPTY_LIST);
  11:     ArrayList verifyList = new ArrayList();
  12:         ...
  13:         list.rotate(i);
  14:         Collections.rotate(verifyList, i);

View Full Code Here

shuffle

public static void shuffle(List list)
Randomly permutes the specified list using a default source of randomness. All permutations occur with approximately equal likelihood.

The hedge "approximately" is used in the foregoing description because default source of randomness is only approximately an unbiased source of independently chosen bits. If it were a perfect source of randomly chosen bits, then the algorithm would choose permutations with perfect uniformity.

This implementation traverses the list backwards, from the last element up to the second, repeatedly swapping a randomly selected element into the "current position". Elements are randomly selected from the portion of the list that runs from the first element to the current position, inclusive.

This method runs in linear time. If the specified list does not implement the RandomAccess interface and is large, this implementation dumps the specified list into an array before shuffling it, and dumps the shuffled array back into the list. This avoids the quadratic behavior that would result from shuffling a "sequential access" list in place.

Parameters:
list - the list to be shuffled.
Throws:
UnsupportedOperationException - if the specified list or its list-iterator does not support the set method.
Usages and Demos :

View More Examples of shuffle(List list)
   1: import java.util.ArrayList;
   2: import java.util.Collections;
   3: import java.util.Comparator;
   4:         ...
   5:         
   6:         Collections.sort(fastest,DOWNLOAD_SPEED_COMPARATOR);
   7:         int numFast = getNumUploads() - 1;
   8:         ...
   9:         
  10:         Collections.shuffle(chokables);
  11:         

View Full Code Here
   1: import java.util.Random;
   2: import java.util.Collections;
   3: public class BlackjackDeck {    
   4:   public BlackjackDeck() {
   5:     this(2);

View Full Code Here
   1: import java.util.Scanner;
   2: import java.util.Collections;
   3: import java.io.FileReader;
   4:         ...
   5: 
   6:         Collections.shuffle(alist);
   7: 
   8:         for (method = 0; method < 2; method++)
   9:         {

View Full Code Here
   1: import java.util.ArrayList;
   2: import java.util.Collections;
   3: import junit.framework.TestCase;
   4:         ...
   5: 
   6:         Collections.reverse(list);
   7:         doOneTest(array(list));
   8:         ...
   9: 
  10:         Collections.shuffle(list);
  11:         doOneTest(array(list));

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: import java.util.Iterator;
   4:         ...
   5: 
   6:         Collections.shuffle(compositeList);
   7: 
   8:         String result = new String();
   9:         for (Iterator iter = compositeList.iterator(); iter.hasNext();) {

View Full Code Here

shuffle

public static void shuffle(List list,
                           Random rnd)
Randomly permute the specified list using the specified source of randomness. All permutations occur with equal likelihood assuming that the source of randomness is fair.

This implementation traverses the list backwards, from the last element up to the second, repeatedly swapping a randomly selected element into the "current position". Elements are randomly selected from the portion of the list that runs from the first element to the current position, inclusive.

This method runs in linear time. If the specified list does not implement the RandomAccess interface and is large, this implementation dumps the specified list into an array before shuffling it, and dumps the shuffled array back into the list. This avoids the quadratic behavior that would result from shuffling a "sequential access" list in place.

Parameters:
list - the list to be shuffled.
rnd - the source of randomness to use to shuffle the list.
Throws:
UnsupportedOperationException - if the specified list or its list-iterator does not support the set operation.
Usages and Demos :

View More Examples of shuffle(List list,Random rnd)
   1:         ArrayList rv = new ArrayList(matches);
   2:         Collections.shuffle(rv, ctx.random());
   3:         if (settings.isInbound())
   4:             rv.add(0, ctx.routerHash());
   5:         else

View Full Code Here
   1:       chars.add(c);
   2:     Collections.shuffle(chars, rand);
   3:     StringBuilder result = new StringBuilder();
   4:     for(char ch : chars)
   5:       result.append(ch);

View Full Code Here
   1:         ArrayList rv = new ArrayList(matches);
   2:         Collections.shuffle(rv, ctx.random());
   3:         if (settings.isInbound())
   4:             rv.add(0, ctx.routerHash());
   5:         else

View Full Code Here
   1: 
   2: import java.util.Collections;
   3: import java.util.List;
   4:         ...
   5:         List peers = sel.selectFloodfillParticipants(_facade.getKBuckets());
   6:         Collections.shuffle(peers, getContext().random());
   7:         if (peers.size() > 0)
   8:             return (Hash)peers.get(0);
   9:         

View Full Code Here
   1:         for (int i = 0; i < ORDER.length; i++) order.add(ORDER[i]);
   2:         Collections.shuffle(order, ctx.random());
   3:         for (int i = 0; i < ORDER.length; i++) {
   4:             int hop = ((Integer)order.get(i)).intValue();
   5:             Hash peer = cfg.getPeer(hop);

View Full Code Here

swap

public static void swap(List list,
                        int i,
                        int j)
Swaps the elements at the specified positions in the specified list. (If the specified positions are equal, invoking this method leaves the list unchanged.)
Parameters:
list - The list in which to swap elements.
i - the index of one element to be swapped.
j - the index of the other element to be swapped.
Throws:
IndexOutOfBoundsException - if either i or j is out of range (i < 0 || i >= list.size() || j < 0 || j >= list.size()).
Since:
1.4
Usages and Demos :

View More Examples of swap(List list,int i,int j)
   1:     print("'list' disjoint (Four)?: " +
   2:       Collections.disjoint(list,
   3:         ...
   4:         Collections.singletonList("Four")));
   5:         ...
   6:     print("max: " + Collections.max(list));
   7:     print("min: " + Collections.min(list));
   8:         ...
   9:     print("copy: " + list);
  10:     Collections.swap(list, 0, list.size() - 1);

View Full Code Here
   1: import java.util.ArrayList;
   2: import java.util.Collections;
   3: import java.util.List;
   4:         ...
   5:         if (index < c.size() - 1) {
   6:             Collections.swap(c, index, index + 1);
   7:             Model.getUseCasesHelper().setExtensionPoints(usecase, c);
   8:         }
   9:     }

View Full Code Here
   1: import java.util.ArrayList;
   2: import java.util.Collections;
   3: import java.util.List;
   4:         ...
   5:         if (index < c.size() - 1) {
   6:             Collections.swap(c, index, index + 1);
   7:             Model.getCoreHelper().setConnections(link, c);
   8:         
   9:         }

View Full Code Here
   1: 
   2: public class Collections {
   3: 
   4:         ...
   5:     private Collections() {}
   6: 
   7:         ...
   8:     public static void sort(List list) {
   9:         java.util.Collections.sort(list);
  10:     }
  11:         ...
  12:     public static void swap(List list, int i, int j) {
  13:         java.util.Collections.swap(list, i, i);

View Full Code Here
   1: import java.util.Collection;
   2: import java.util.Collections;
   3: import java.util.Iterator;
   4:         ...
   5:   {
   6:     XList list = createXList(Collections.EMPTY_LIST);
   7:     ArrayList verifyList = new ArrayList();
   8:         ...
   9:   {
  10:     XList list = createXList(Collections.EMPTY_LIST);
  11:     ArrayList verifyList = new ArrayList();
  12:         ...
  13:     ArrayList verifyList = new ArrayList(elements);
  14:     Collections.swap(verifyList, a, b);    

View Full Code Here

void copy

public static  void copy(T> dest,
                            T> src)
Copies all of the elements from one list into another. After the operation, the index of each copied element in the destination list will be identical to its index in the source list. The destination list must be at least as long as the source list. If it is longer, the remaining elements in the destination list are unaffected.

This method runs in linear time.

Parameters:
dest - The destination list.
src - The source list.
Throws:
IndexOutOfBoundsException - if the destination list is too small to contain the entire source List.
UnsupportedOperationException - if the destination list's list-iterator does not support the set operation.

void fill

public static  void fill(T> list,
                            T obj)
Replaces all of the elements of the specified list with the specified element.

This method runs in linear time.

Parameters:
list - the list to be filled with the specified element.
obj - The element with which to fill the specified list.
Throws:
UnsupportedOperationException - if the specified list or its list-iterator does not support the set operation.

void sort

public static  void sort(List list,
                            T> c)
Sorts the specified list according to the order induced by the specified comparator. All elements in the list must be mutually comparable using the specified comparator (that is, c.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the list).

This sort is guaranteed to be stable: equal elements will not be reordered as a result of the sort.

The sorting algorithm is a modified mergesort (in which the merge is omitted if the highest element in the low sublist is less than the lowest element in the high sublist). This algorithm offers guaranteed n log(n) performance. The specified list must be modifiable, but need not be resizable. This implementation dumps the specified list into an array, sorts the array, and iterates over the list resetting each element from the corresponding position in the array. This avoids the n2 log(n) performance that would result from attempting to sort a linked list in place.

Parameters:
list - the list to be sorted.
c - the comparator to determine the order of the list. A null value indicates that the elements' natural ordering should be used.
Throws:
ClassCastException - if the list contains elements that are not mutually comparable using the specified comparator.
UnsupportedOperationException - if the specified list's list-iterator does not support the set operation.
See Also:
Comparator