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SUMMARY: JavaDoc of java.util.Set JAVADOC | Sourc code of java.util.Set SOURCE | Download java.util.Set DOWNLOAD | NESTED | FIELD | CONSTR | METHOD DETAIL: FIELD | CONSTR | METHOD

java.util
Interface Set  view Set download Set.java

All Superinterfaces:
Collection, java.lang.Iterable
All Known Subinterfaces:
SortedSet
All Known Implementing Classes:
AbstractSet, Collections.SynchronizedSet, Collections.SynchronizedSortedSet, Collections.UnmodifiableSet, Collections.UnmodifiableSortedSet, HashSet, LinkedHashSet, TreeSet
public interface Set
extends Collection

A collection that contains no duplicates. In other words, for two set elements e1 and e2, e1.equals(e2) returns false. There are additional stipulations on add, equals and hashCode, as well as the requirements that constructors do not permit duplicate elements. The Set interface is incompatible with List; you cannot implement both simultaneously.

Note: Be careful about using mutable objects in sets. In particular, if a mutable object changes to become equal to another set element, you have violated the contract. As a special case of this, a Set is not allowed to be an element of itself, without risking undefined behavior.

Since:
1.2

Method Summary
 boolean add(java.lang.Object o)
          Adds the specified element to the set if it is not already present (optional operation).
 boolean addAll(Collection c)
          Adds all of the elements of the given collection to this set (optional operation).
 void clear()
          Removes all elements from this set (optional operation).
 boolean contains(java.lang.Object o)
          Returns true if the set contains the specified element.
 boolean containsAll(Collection c)
          Returns true if this set contains all elements in the specified collection.
 boolean equals(java.lang.Object o)
          Compares the specified object to this for equality.
 int hashCode()
          Returns the hash code for this set.
 boolean isEmpty()
          Returns true if the set contains no elements.
 Iterator iterator()
          Returns an iterator over the set.
 boolean remove(java.lang.Object o)
          Removes the specified element from this set (optional operation).
 boolean removeAll(Collection c)
          Removes from this set all elements contained in the specified collection (optional operation).
 boolean retainAll(Collection c)
          Retains only the elements in this set that are also in the specified collection (optional operation).
 int size()
          Returns the number of elements in the set.
 java.lang.Object[] toArray()
          Returns an array containing the elements of this set.
 java.lang.Object[] toArray(java.lang.Object[] a)
          Returns an array containing the elements of this set, of the same runtime type of the argument.
 

Method Detail

add

public boolean add(java.lang.Object o)
Adds the specified element to the set if it is not already present (optional operation). In particular, the comparison algorithm is o == null ? e == null : o.equals(e). Sets need not permit all values, and may document what exceptions will be thrown if a value is not permitted.

Specified by:
add in interface Collection

addAll

public boolean addAll(Collection c)
Adds all of the elements of the given collection to this set (optional operation). If the argument is also a Set, this returns the mathematical union of the two. The behavior is unspecified if the set is modified while this is taking place.

Specified by:
addAll in interface Collection

clear

public void clear()
Removes all elements from this set (optional operation). This set will be empty afterwords, unless an exception occurs.

Specified by:
clear in interface Collection

contains

public boolean contains(java.lang.Object o)
Returns true if the set contains the specified element. In other words, this looks for o == null ? e == null : o.equals(e).

Specified by:
contains in interface Collection

containsAll

public boolean containsAll(Collection c)
Returns true if this set contains all elements in the specified collection. If the argument is also a set, this is the subset relationship.

Specified by:
containsAll in interface Collection

equals

public boolean equals(java.lang.Object o)
Compares the specified object to this for equality. For sets, the object must be a set, the two must have the same size, and every element in one must be in the other.

Specified by:
equals in interface Collection

hashCode

public int hashCode()
Returns the hash code for this set. In order to satisfy the contract of equals, this is the sum of the hashcode of all elements in the set.

Specified by:
hashCode in interface Collection

isEmpty

public boolean isEmpty()
Returns true if the set contains no elements.

Specified by:
isEmpty in interface Collection

iterator

public Iterator iterator()
Returns an iterator over the set. The iterator has no specific order, unless further specified.

Specified by:
iterator in interface Collection

remove

public boolean remove(java.lang.Object o)
Removes the specified element from this set (optional operation). If an element e exists, o == null ? e == null : o.equals(e), it is removed from the set.

Specified by:
remove in interface Collection

removeAll

public boolean removeAll(Collection c)
Removes from this set all elements contained in the specified collection (optional operation). If the argument is a set, this returns the asymmetric set difference of the two sets.

Specified by:
removeAll in interface Collection

retainAll

public boolean retainAll(Collection c)
Retains only the elements in this set that are also in the specified collection (optional operation). If the argument is also a set, this performs the intersection of the two sets.

Specified by:
retainAll in interface Collection

size

public int size()
Returns the number of elements in the set. If there are more than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE. This is the cardinality of the set.

Specified by:
size in interface Collection

toArray

public java.lang.Object[] toArray()
Returns an array containing the elements of this set. If the set makes a guarantee about iteration order, the array has the same order. The array is distinct from the set; modifying one does not affect the other.

Specified by:
toArray in interface Collection

toArray

public java.lang.Object[] toArray(java.lang.Object[] a)
Returns an array containing the elements of this set, of the same runtime type of the argument. If the given set is large enough, it is reused, and null is inserted in the first unused slot. Otherwise, reflection is used to build a new array. If the set makes a guarantee about iteration order, the array has the same order. The array is distinct from the set; modifying one does not affect the other.

Specified by:
toArray in interface Collection
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Home >> All >> java >> [ util overview ]  PREV CLASS  NEXT CLASS
SUMMARY: JavaDoc of java.util.Set JAVADOC | Sourc code of java.util.Set SOURCE | Download java.util.Set DOWNLOAD | NESTED | FIELD | CONSTR | METHOD DETAIL: FIELD | CONSTR | METHOD