E
- the type of elements maintained by this setIterable<E>
, Collection<E>
, Set<E>
ConcurrentSkipListSet
, CopyOnWriteArraySet
, EnumSet
, HashSet
, TreeSet
public abstract class AbstractSet<E> extends AbstractCollection<E> implements Set<E>
Set
interface to minimize the effort required to implement this interface. The process of implementing a set by extending this class is identical to that of implementing a Collection by extending AbstractCollection, except that all of the methods and constructors in subclasses of this class must obey the additional constraints imposed by the Set
interface (for instance, the add method must not permit addition of multiple instances of an object to a set).
Note that this class does not override any of the implementations from the AbstractCollection
class. It merely adds implementations for equals
and hashCode
.
This class is a member of the Java Collections Framework.
Modifier | Constructor | Description |
---|---|---|
protected |
Sole constructor. |
Modifier and Type | Method | Description |
---|---|---|
boolean |
equals |
Compares the specified object with this set for equality. |
int |
hashCode() |
Returns the hash code value for this set. |
boolean |
removeAll |
Removes from this set all of its elements that are contained in the specified collection (optional operation). |
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, retainAll, toArray, toArray, toString
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
parallelStream, removeIf, stream, toArray
protected AbstractSet()
public boolean equals(Object o)
true
if the given object is also a set, the two sets have the same size, and every member of the given set is contained in this set. This ensures that the equals
method works properly across different implementations of the Set
interface. This implementation first checks if the specified object is this set; if so it returns true
. Then, it checks if the specified object is a set whose size is identical to the size of this set; if not, it returns false. If so, it returns containsAll((Collection) o)
.
public int hashCode()
null
element is defined to be zero. This ensures that s1.equals(s2)
implies that s1.hashCode()==s2.hashCode()
for any two sets s1
and s2
, as required by the general contract of Object.hashCode()
. This implementation iterates over the set, calling the hashCode
method on each element in the set, and adding up the results.
public boolean removeAll(Collection<?> c)
This implementation determines which is the smaller of this set and the specified collection, by invoking the size
method on each. If this set has fewer elements, then the implementation iterates over this set, checking each element returned by the iterator in turn to see if it is contained in the specified collection. If it is so contained, it is removed from this set with the iterator's remove
method. If the specified collection has fewer elements, then the implementation iterates over the specified collection, removing from this set each element returned by the iterator, using this set's remove
method.
Note that this implementation will throw an UnsupportedOperationException
if the iterator returned by the iterator
method does not implement the remove
method.
removeAll
in interface Collection<E>
removeAll
in interface Set<E>
removeAll
in class AbstractCollection<E>
c
- collection containing elements to be removed from this settrue
if this set changed as a result of the callUnsupportedOperationException
- if the removeAll
operation is not supported by this setClassCastException
- if the class of an element of this set is incompatible with the specified collection (optional)NullPointerException
- if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/AbstractSet.html