File	Doc	Category	Size	Date	Package
Set.java	API Doc	Java SE 5 API	14702	Fri Aug 26 14:57:24 BST 2005	java.util

Set

Fields Summary

Constructors Summary

Methods Summary
public boolean	add(E o) Adds the specified element to this set if it is not already present (optional operation). More formally, adds the specified element, o, to this set if this set contains no element e such that (o==null ? e==null : o.equals(e)). If this set already contains the specified element, the call leaves this set unchanged and returns false. In combination with the restriction on constructors, this ensures that sets never contain duplicate elements. The stipulation above does not imply that sets must accept all elements; sets may refuse to add any particular element, including null, and throwing an exception, as described in the specification for Collection.add. Individual set implementations should clearly document any restrictions on the elements that they may contain. param o element to be added to this set. return true if this set did not already contain the specified element. throws UnsupportedOperationException if the add method is not supported by this set. throws ClassCastException if the class of the specified element prevents it from being added to this set. throws NullPointerException if the specified element is null and this set does not support null elements. throws IllegalArgumentException if some aspect of the specified element prevents it from being added to this set.
public boolean	addAll(java.util.Collection c) Adds all of the elements in the specified collection to this set if they're not already present (optional operation). If the specified collection is also a set, the addAll operation effectively modifies this set so that its value is the union of the two sets. The behavior of this operation is unspecified if the specified collection is modified while the operation is in progress. param c collection whose elements are to be added to this set. return true if this set changed as a result of the call. throws UnsupportedOperationException if the addAll method is not supported by this set. throws ClassCastException if the class of some element of the specified collection prevents it from being added to this set. throws NullPointerException if the specified collection contains one or more null elements and this set does not support null elements, or if the specified collection is null. throws IllegalArgumentException if some aspect of some element of the specified collection prevents it from being added to this set. see #add(Object)
public void	clear() Removes all of the elements from this set (optional operation). This set will be empty after this call returns (unless it throws an exception). throws UnsupportedOperationException if the clear method is not supported by this set.
public boolean	contains(java.lang.Object o) Returns true if this set contains the specified element. More formally, returns true if and only if this set contains an element e such that (o==null ? e==null : o.equals(e)). param o element whose presence in this set is to be tested. return true if this set contains the specified element. throws ClassCastException if the type of the specified element is incompatible with this set (optional). throws NullPointerException if the specified element is null and this set does not support null elements (optional).
public boolean	containsAll(java.util.Collection c) Returns true if this set contains all of the elements of the specified collection. If the specified collection is also a set, this method returns true if it is a subset of this set. param c collection to be checked for containment in this set. return true if this set contains all of the elements of the specified collection. throws ClassCastException if the types of one or more elements in the specified collection are incompatible with this set (optional). throws NullPointerException if the specified collection contains one or more null elements and this set does not support null elements (optional). throws NullPointerException if the specified collection is null. see #contains(Object)
public boolean	equals(java.lang.Object o) Compares the specified object with this set for equality. Returns true if the specified object is also a set, the two sets have the same size, and every member of the specified set is contained in this set (or equivalently, every member of this set is contained in the specified set). This definition ensures that the equals method works properly across different implementations of the set interface. param o Object to be compared for equality with this set. return true if the specified Object is equal to this set.
public int	hashCode() Returns the hash code value for this set. The hash code of a set is defined to be the sum of the hash codes of the elements in the set, where the hashcode of a null element is defined to be zero. This ensures that s1.equals(s2) implies that s1.hashCode()==s2.hashCode() for any two sets s1 and s2, as required by the general contract of the Object.hashCode method. return the hash code value for this set. see Object#hashCode() see Object#equals(Object) see Set#equals(Object)
public boolean	isEmpty() Returns true if this set contains no elements. return true if this set contains no elements.
public java.util.Iterator	iterator() Returns an iterator over the elements in this set. The elements are returned in no particular order (unless this set is an instance of some class that provides a guarantee). return an iterator over the elements in this set.
public boolean	remove(java.lang.Object o) Removes the specified element from this set if it is present (optional operation). More formally, removes an element e such that (o==null ? e==null : o.equals(e)), if the set contains such an element. Returns true if the set contained the specified element (or equivalently, if the set changed as a result of the call). (The set will not contain the specified element once the call returns.) param o object to be removed from this set, if present. return true if the set contained the specified element. throws ClassCastException if the type of the specified element is incompatible with this set (optional). throws NullPointerException if the specified element is null and this set does not support null elements (optional). throws UnsupportedOperationException if the remove method is not supported by this set.
public boolean	removeAll(java.util.Collection c) Removes from this set all of its elements that are contained in the specified collection (optional operation). If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets. param c collection that defines which elements will be removed from this set. return true if this set changed as a result of the call. throws UnsupportedOperationException if the removeAll method is not supported by this Collection. throws ClassCastException if the types of one or more elements in this set are incompatible with the specified collection (optional). throws NullPointerException if this set contains a null element and the specified collection does not support null elements (optional). throws NullPointerException if the specified collection is null. see #remove(Object)
public boolean	retainAll(java.util.Collection c) Retains only the elements in this set that are contained in the specified collection (optional operation). In other words, removes from this set all of its elements that are not contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the intersection of the two sets. param c collection that defines which elements this set will retain. return true if this collection changed as a result of the call. throws UnsupportedOperationException if the retainAll method is not supported by this Collection. throws ClassCastException if the types of one or more elements in this set are incompatible with the specified collection (optional). throws NullPointerException if this set contains a null element and the specified collection does not support null elements (optional). throws NullPointerException if the specified collection is null. see #remove(Object)
public int	size() Returns the number of elements in this set (its cardinality). If this set contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE. return the number of elements in this set (its cardinality).
public java.lang.Object[]	toArray() Returns an array containing all of the elements in this set. Obeys the general contract of the Collection.toArray method. return an array containing all of the elements in this set.
public T[]	toArray(T[] a) Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array. Obeys the general contract of the Collection.toArray(Object[]) method. param a the array into which the elements of this set are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose. return an array containing the elements of this set. throws ArrayStoreException the runtime type of a is not a supertype of the runtime type of every element in this set. throws NullPointerException if the specified array is null.