Java.util.HashSet类

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The java.util.HashSet class implements the Set interface, backed by a hash table.Following are the important points about HashSet:

This class makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time.
This class permits the null element.

类声明

以下是声明java.util.HashSet class:

public class HashSet<E>
   extends AbstractSet<E>
      implements Set<E>, Cloneable, Serializable

Following is the parameter for java.util.HashSet class:

S.N.	构造方法 & 详细描述
1	HashSet() This constructs a new, empty set; the backing HashMap instance has default initial capacity (16) and load factor (0.75).
2	HashSet(Collection<? extends E> c) This constructs a new set containing the elements in the specified collection.
3	HashSet(int initialCapacity) This constructs a new, empty set; the backing HashMap instance has the specified initial capacity and default load factor (0.75).
4	HashSet(int initialCapacity, float loadFactor) This constructs a new, empty set; the backing HashMap instance has the specified initial capacity and the specified load factor.

S.N.	方法 & 描述
1	boolean add(E e) This method adds the specified element to this set if it is not already present.
2	void clear() This method removes all of the elements from this set.
3	Object clone() This method returns a shallow copy of this HashSet instance, the elements themselves are not cloned.
4	boolean contains(Object o) This method returns true if this set contains the specified element.
5	boolean isEmpty() This method returns true if this set contains no elements.
6	Iterator<E> iterator() This method returns an iterator over the elements in this set.
7	boolean remove(Object o) This method removes the specified element from this set if it is present.
8	int size() This method returns returns the number of elements in this set(its cardinality).

此类从以下类继承了上面列出的方法

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