java.util.AbstractSet Maven / Gradle / Ivy
/*
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This work corresponds to the API signatures of JSR 219: Foundation
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*/
package java.util;
/**
* This class provides a skeletal implementation of the 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 intances 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.
*
* @author Josh Bloch
* @version 1.14, 02/02/00
* @see Collection
* @see AbstractCollection
* @see Set
* @since 1.2
*/
public abstract class AbstractSet extends AbstractCollection implements Set
{
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
protected AbstractSet() { }
/**
* Compares the specified object with this set for equality. Returns
* 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 it returns false. If so, it returns
* containsAll((Collection) o).
*
* @param o Object to be compared for equality with this set.
* @return true if the specified object is equal to this set.
*/
public boolean equals(Object o) {
return false;
}
/**
* 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.
* 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 enumerates over the set, calling the
* hashCode method on each element in the collection, and
* adding up the results.
*
* @return the hash code value for this set.
*/
public int hashCode() {
return 0;
}
/**
* Removes from this set all of its elements that are contained in
* the specified collection (optional operation).
*
* 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.
*
* @param c elements to be removed from this set.
* @return true if this set changed as a result of the call.
*
* @throws UnsupportedOperationException removeAll is not supported
* by this set.
* @throws NullPointerException if the specified collection is null.
* @see #remove(Object)
* @see #contains(Object)
*/
public boolean removeAll(Collection c) {
return false;
}
}