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 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(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(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.