 Known Direct Subclasses
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Class Overview
HashSet is an implementation of a Set. All optional operations (adding and
removing) are supported. The elements can be any objects.
Summary
| Public Constructors |
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HashSet()
Constructs a new empty instance of HashSet.
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HashSet(int capacity)
Constructs a new instance of HashSet with the specified capacity.
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HashSet(int capacity, float loadFactor)
Constructs a new instance of HashSet with the specified capacity and
load factor.
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HashSet(Collection<? extends E> collection)
Constructs a new instance of HashSet containing the unique elements
in the specified collection.
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| Public Methods |
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boolean
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add(Object object)
Adds the specified object to this HashSet if not already present.
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void
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clear()
Removes all elements from this HashSet, leaving it empty.
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boolean
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contains(Object object)
Searches this HashSet for the specified object.
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boolean
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isEmpty()
Returns true if this HashSet has no elements, false otherwise.
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Iterator<E>
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iterator()
Returns an Iterator on the elements of this HashSet.
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boolean
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remove(Object object)
Removes the specified object from this HashSet.
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int
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size()
Returns the number of elements in this HashSet.
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[Expand]
Inherited Methods |
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From class
java.util.AbstractSet
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boolean
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equals(Object object)
Compares the specified object to this Set and returns true if they are equal.
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int
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hashCode()
Returns the hash code for this set.
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boolean
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removeAll(Collection<?> collection)
Removes all occurrences in this collection which are contained in the
specified collection.
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From class
java.util.AbstractCollection
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boolean
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add(E object)
Attempts to add object to the contents of this Collection
(optional).
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boolean
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addAll(Collection<? extends E> collection)
Attempts to add all of the objects contained in collection to the
contents of this Collection (optional).
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void
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clear()
Removes all elements from this Collection, leaving it empty
(optional).
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boolean
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contains(Object object)
Tests whether this Collection contains the specified object.
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boolean
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containsAll(Collection<?> collection)
Tests whether this Collection contains all objects contained in the
specified Collection.
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boolean
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isEmpty()
Returns if this Collection contains no elements.
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abstract
Iterator<E>
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iterator()
Returns an instance of Iterator that may be used to access the
objects contained by this Collection. |
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boolean
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remove(Object object)
Removes one instance of the specified object from this Collection if
one is contained (optional).
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boolean
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removeAll(Collection<?> collection)
Removes all occurrences in this Collection of each object in the
specified Collection (optional).
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boolean
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retainAll(Collection<?> collection)
Removes all objects from this Collection that are not also found in
the Collection passed (optional).
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abstract
int
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size()
Returns a count of how many objects this Collection contains.
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Object[]
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toArray()
Returns a new array containing all elements contained in this
ArrayList.
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String
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toString()
Returns the string representation of this Collection.
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From class
java.lang.Object
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boolean
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equals(Object obj)
Indicates whether some other object is "equal to" this one.
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final
Class<?>
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getClass()
Returns the runtime class of an object.
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int
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hashCode()
Returns a hash code value for the object.
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final
void
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notify()
Wakes up a single thread that is waiting on this object's monitor.
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final
void
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notifyAll()
Wakes up all threads that are waiting on this object's monitor.
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String
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toString()
Returns a string representation of the object.
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final
void
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wait(long timeout, int nanos)
Causes current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object, or some other
thread interrupts the current thread, or a certain amount of real time has
elapsed. |
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final
void
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wait(long timeout)
Causes current thread to wait until either another thread invokes the
notify() method or the
notifyAll() method for this object, or a specified
amount of time has elapsed. |
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final
void
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wait()
Causes current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object. |
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From interface
java.lang.Iterable
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From interface
java.util.Collection
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abstract
boolean
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add(E object)
Attempts to add object to the contents of this Collection
(optional).
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abstract
boolean
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addAll(Collection<? extends E> collection)
Attempts to add all of the objects contained in Collection to the
contents of this Collection (optional).
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abstract
void
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clear()
Removes all elements from this Collection, leaving it empty
(optional).
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abstract
boolean
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contains(Object object)
Tests whether this Collection contains the specified object.
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abstract
boolean
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containsAll(Collection<?> collection)
Tests whether this Collection contains all objects contained in the
specified Collection.
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abstract
boolean
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equals(Object object)
Compares the argument to the receiver, and returns true if they represent the
same object using a class specific comparison.
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abstract
int
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hashCode()
Returns an integer hash code for the receiver.
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abstract
boolean
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isEmpty()
Returns if this Collection contains no elements.
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abstract
Iterator<E>
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iterator()
Returns an instance of Iterator that may be used to access the
objects contained by this Collection. |
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abstract
boolean
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remove(Object object)
Removes one instance of the specified object from this Collection if
one is contained (optional).
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abstract
boolean
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removeAll(Collection<?> collection)
Removes all occurrences in this Collection of each object in the
specified Collection (optional).
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abstract
boolean
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retainAll(Collection<?> collection)
Removes all objects from this Collection that are not also found in
the Collection passed (optional).
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abstract
int
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size()
Returns a count of how many objects this Collection contains.
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abstract
<T>
T[]
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toArray(T[] a)
Returns an array containing all of the elements in this collection; the
runtime type of the returned array is that of the specified array.
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abstract
Object[]
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toArray()
Returns an array containing all of the elements in this collection.
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From interface
java.util.Set
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abstract
boolean
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add(E object)
Adds the specified object to this set.
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abstract
boolean
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addAll(Collection<? extends E> collection)
Adds the objects in the specified collection which do not exist yet in this
set.
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abstract
void
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clear()
Removes all elements from this set, leaving it empty.
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abstract
boolean
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contains(Object object)
Searches this set for the specified object.
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abstract
boolean
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containsAll(Collection<?> collection)
Searches this set for all objects in the specified collection.
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abstract
boolean
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equals(Object object)
Compares the specified object to this set, and returns true if they represent
the same object using a class specific comparison.
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abstract
int
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hashCode()
Returns the hash code for this set.
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abstract
boolean
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isEmpty()
Returns true if this set has no elements.
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abstract
Iterator<E>
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iterator()
Returns an iterator on the elements of this set.
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abstract
boolean
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remove(Object object)
Removes the specified object from this set.
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abstract
boolean
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removeAll(Collection<?> collection)
Removes all objects in the specified collection from this set.
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abstract
boolean
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retainAll(Collection<?> collection)
Removes all objects from this set that are not contained in the specified
collection.
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abstract
int
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size()
Returns the number of elements in this set.
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abstract
Object[]
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toArray()
Returns an array containing all elements contained in this set.
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Public Constructors
public
HashSet
()
Constructs a new empty instance of HashSet.
public
HashSet
(int capacity)
Constructs a new instance of HashSet with the specified capacity.
Parameters
| capacity |
the initial capacity of this 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.
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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.
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Public Methods
public
boolean
add
(Object object)
Adds the specified object to this HashSet if not already present.
Parameters
| object |
the object to add. |
Returns
true when this HashSet did not already contain the
object, false otherwise
public
void
clear
()
Removes all elements from this HashSet, leaving it empty.
public
boolean
contains
(Object object)
Searches this HashSet for the specified object.
Parameters
| object |
the object to search for. |
Returns
true if object is an element of this HashSet,
false otherwise.
public
boolean
isEmpty
()
Returns true if this HashSet has no elements, false otherwise.
Returns
true if this HashSet has no elements, false
otherwise.
public
Iterator<E>
iterator
()
Returns an Iterator on the elements of this HashSet.
Returns
- an Iterator on the elements of this
HashSet.
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.
public
int
size
()
Returns the number of elements in this HashSet.
Returns
- the number of elements in this
HashSet.