 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(E 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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Object
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clone()
Returns a new HashSet with the same elements and size as this
HashSet.
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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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<T>
T[]
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toArray(T[] contents)
Returns an array containing all elements contained in this Collection.
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Object[]
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toArray()
Returns a new array containing all elements contained in this Collection.
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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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Object
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clone()
Creates and returns a copy of this Object.
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boolean
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equals(Object o)
Compares this instance with the specified object and indicates if they
are equal.
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void
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finalize()
Invoked when the garbage collector has detected that this instance is no longer reachable.
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final
Class<?>
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getClass()
Returns the unique instance of Class that represents this
object's class. |
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int
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hashCode()
Returns an integer hash code for this object.
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final
void
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notify()
Causes a thread which is waiting on this object's monitor (by means of
calling one of the wait() methods) to be woken up.
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final
void
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notifyAll()
Causes all threads which are waiting on this object's monitor (by means
of calling one of the wait() methods) to be woken up.
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String
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toString()
Returns a string containing a concise, human-readable description of this
object.
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final
void
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wait()
Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.
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final
void
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wait(long millis, int nanos)
Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the
specified timeout expires.
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final
void
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wait(long millis)
Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the
specified timeout expires.
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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[] array)
Returns an array containing all elements contained in this Collection.
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abstract
Object[]
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toArray()
Returns a new array containing all elements contained 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
<T>
T[]
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toArray(T[] array)
Returns an array containing all elements contained 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.
|
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.
|
Public Methods
public
boolean
add
(E 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
Object
clone
()
Returns a new HashSet with the same elements and size as this
HashSet.
Returns
- a shallow copy of this
HashSet.
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.
