Collections.EmptySet

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java.util
Class Collections.EmptySet

java.lang.Object
  java.util.AbstractCollection
      java.util.AbstractSet
          java.util.Collections.EmptySet

All Implemented Interfaces:: Collection, java.lang.Iterable, java.io.Serializable, Set

Enclosing class:: Collections

private static final class Collections.EmptySet
extends AbstractSet
implements java.io.Serializable

The implementation of Collections.EMPTY_SET 55 . This class name is required for compatibility with Sun's JDK serializability.

Field Summary

private static long serialVersionUID
          Compatible with JDK 1.4.

Constructor Summary

(package private) Collections.EmptySet()
          A private constructor adds overhead.

Method Summary

boolean contains(java.lang.Object o)
          The empty set never contains anything.

boolean containsAll(Collection c)
          This is true only if the given collection is also empty.

boolean equals(java.lang.Object o)
          Equal only if the other set is empty.

int hashCode()
          The hashcode is always 0.

Iterator iterator()
          Returns an iterator that does not iterate.

boolean remove(java.lang.Object o)
          Always succeeds with a false result.

boolean removeAll(Collection c)
          Always succeeds with a false result.

boolean retainAll(Collection c)
          Always succeeds with a false result.

int size()
          The size: always 0!

java.lang.Object[] toArray()
          The array is always empty.

java.lang.Object[] toArray(java.lang.Object[] a)
          We don't even need to use reflection!

java.lang.String toString()
          The string never changes.

Methods inherited from class java.util.AbstractCollection

add, addAll, clear, equals, hashCode, isEmpty, removeAllInternal, retainAllInternal

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Set

add, addAll, clear, isEmpty

Field Detail

serialVersionUID

private static final long serialVersionUID

Compatible with JDK 1.4.

See Also:: Constant Field Values

Constructor Detail