- Type Parameters:
E- the type of elements maintained by this set
public abstract class AbstractSet<E> extends AbstractCollection<E> implements Set<E>This class provides a skeletal implementation of the
Setinterface 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
Setinterface (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
AbstractCollectionclass. It merely adds implementations for
This class is a member of the Java Collections Framework.
Constructors Modifier Constructor Description
Modifier and Type Method Description
equals(Object o)Compares the specified object with this set for equality.
hashCode()Returns the hash code value for this set.
removeAll(Collection<?> c)Removes from this set all of its elements that are contained in the specified collection (optional operation).
Methods declared in class java.util.AbstractCollection
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, retainAll, toArray, toArray, toString
Methods declared in class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
public boolean equals(Object o)Compares the specified object with this set for equality. Returns
trueif 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
equalsmethod works properly across different implementations of the
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
public int hashCode()Returns the hash code value for this set. The hash code of a set is defined to be the sum of the hash codes of the elements in the set, where the hash code of a
nullelement is defined to be zero. This ensures that
s1.hashCode()==s2.hashCode()for any two sets
s2, as required by the general contract of
This implementation iterates over the set, calling the
hashCodemethod on each element in the set, and adding up the results.
public boolean removeAll(Collection<?> c)Removes from this set all of its elements that are contained in the specified collection (optional operation). If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.
This implementation determines which is the smaller of this set and the specified collection, by invoking the
sizemethod 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
removemethod. 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
Note that this implementation will throw an
UnsupportedOperationExceptionif the iterator returned by the
iteratormethod does not implement the
- Specified by:
- Specified by:
c- collection containing elements to be removed from this set
trueif this set changed as a result of the call
UnsupportedOperationException- if the
removeAlloperation is not supported by this set
ClassCastException- 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
- See Also: