java.lang.ref.Reference Maven / Gradle / Ivy

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This work corresponds to the API signatures of JSR 219: Foundation
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package java.lang.ref;

/** 
 * Abstract base class for reference objects.  This class defines the
 * operations common to all reference objects.	Because reference objects are
 * implemented in close cooperation with the garbage collector, this class may
 * not be subclassed directly.
 *
 * @version  1.35 08/27/01
 * @author   Mark Reinhold
 * @since    1.2
 */
public abstract class Reference
{

    Reference(Object referent) { }

    Reference(Object referent, ReferenceQueue queue) { }

    /** 
     * Returns this reference object's referent.  If this reference object has
     * been cleared, either by the program or by the garbage collector, then
     * this method returns null.
     *
     * @return	 The object to which this reference refers, or
     *		 null if this reference object has been cleared
     */
    public Object get() {
        return null;
    }

    /** 
     * Clears this reference object.  Invoking this method will not cause this
     * object to be enqueued.
     */
    public void clear() { }

    /** 
     * Tells whether or not this reference object has been enqueued, either by
     * the program or by the garbage collector.	 If this reference object was
     * not registered with a queue when it was created, then this method will
     * always return false.
     *
     * @return	 true if and only if this reference object has
     *		 been enqueued
     */
    public boolean isEnqueued() {
        return false;
    }

    /** 
     * Adds this reference object to the queue with which it is registered,
     * if any.
     *
     * @return	 true if this reference object was successfully
     *		 enqueued; false if it was already enqueued or if
     *		 it was not registered with a queue when it was created
     */
    public boolean enqueue() {
        return false;
    }
}