Class HashSet<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractSet<E>
java.util.HashSet<E>
All Implemented Interfaces:
Iterable<E>, Collection<E>, Set<E>
Direct Known Subclasses:
LinkedHashSet
public class HashSet<E> extends AbstractSet<E> implements Set<E>
HashSet is an implementation of a Set. All optional operations (adding and removing) are supported. The elements can be any objects.

  • Constructor Summary

    Constructors
    Constructor
    Description
    HashSet()
    Constructs a new empty instance of HashSet.
    HashSet(int capacity)
    Constructs a new instance of HashSet with the specified capacity.
    HashSet(int capacity, float loadFactor)
    Constructs a new instance of HashSet with the specified capacity and load factor.
    HashSet(Collection<? extends E> collection)
    Constructs a new instance of HashSet containing the unique elements in the specified collection.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(E object)
    Adds the specified object to this HashSet if not already present.
    void
    clear()
    Removes all elements from this HashSet, leaving it empty.
    boolean
    contains(java.lang.Object object)
    Searches this HashSet for the specified object.
    boolean
    isEmpty()
    Returns true if this HashSet has no elements, false otherwise.
    Iterator<E>
    iterator()
    Returns an Iterator on the elements of this HashSet.
    boolean
    remove(java.lang.Object object)
    Removes the specified object from this HashSet.
    int
    size()
    Returns the number of elements in this HashSet.

    Methods inherited from class AbstractSet

    equals, hashCode, removeAll

    Methods inherited from class AbstractCollection

    addAll, containsAll, retainAll, toArray, toArray, toString

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

    Methods inherited from interface Collection

    removeIf

    Methods inherited from interface Iterable

    forEach

    Methods inherited from interface Set

    addAll, containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray

  • Constructor Details

    • HashSet

      public HashSet()
      Constructs a new empty instance of HashSet.

    • HashSet

      public HashSet(int capacity)

      Constructs a new instance of HashSet with the specified capacity.

      Parameters
      • capacity: the initial capacity of this HashSet.

    • HashSet

      public HashSet(int capacity, float loadFactor)

      Constructs a new instance of HashSet with the specified capacity and load factor.

      Parameters

      • capacity: the initial capacity.

      • loadFactor: the initial load factor.

    • HashSet

      public HashSet(Collection<? extends E> collection)

      Constructs a new instance of HashSet containing the unique elements in the specified collection.

      Parameters
      • collection: the collection of elements to add.

  • Method Details

    • add

      public boolean add(E object)

      Adds the specified object to this HashSet if not already present.

      Parameters
      • object: the object to add.
      Returns
      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface Set<E>
      Overrides:
      add in class AbstractCollection<E>
      Returns:
      true when this HashSet did not already contain the object, false otherwise

    • clear

      public void clear()

      Removes all elements from this HashSet, leaving it empty.

      See also

      • #isEmpty

      • #size

      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface Set<E>
      Overrides:
      clear in class AbstractCollection<E>

    • contains

      public boolean contains(java.lang.Object object)

      Searches this HashSet for the specified object.

      Parameters
      • object: the object to search for.
      Returns
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface Set<E>
      Overrides:
      contains in class AbstractCollection<E>
      Returns:
      true if object is an element of this HashSet, false otherwise.

    • isEmpty

      public boolean isEmpty()

      Returns true if this HashSet has no elements, false otherwise.

      Returns
      Specified by:
      isEmpty in interface Collection<E>
      Specified by:
      isEmpty in interface Set<E>
      Overrides:
      isEmpty in class AbstractCollection<E>
      Returns:

      true if this HashSet has no elements, false otherwise.

      See also
      • #size

    • iterator

      public Iterator<E> iterator()

      Returns an Iterator on the elements of this HashSet.

      Returns

      an Iterator on the elements of this HashSet.

      See also
      • Iterator
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface Set<E>
      Specified by:
      iterator in class AbstractCollection<E>

    • remove

      public boolean remove(java.lang.Object object)

      Removes the specified object from this HashSet.

      Parameters
      • object: the object to remove.
      Returns

      true if the object was removed, false otherwise.

      Specified by:
      remove in interface Collection<E>
      Specified by:
      remove in interface Set<E>
      Overrides:
      remove in class AbstractCollection<E>
      Returns:

      true if this Collection is modified, false otherwise.

      Throws

      • UnsupportedOperationException: if removing from this Collection is not supported.

      • ClassCastException: if the object passed is not of the correct type.

      • NullPointerException: @throws NullPointerException if object is null and this Collection doesn't support null elements.

    • size

      public int size()

      Returns the number of elements in this HashSet.

      Returns

      the number of elements in this HashSet.

      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface Set<E>
      Specified by:
      size in class AbstractCollection<E>
      Returns:
      how many objects this Collection contains, or Integer.MAX_VALUE if there are more than Integer.MAX_VALUE elements in this Collection.