(ref) Weak reference created with null referent cannot be enqueued

Name: akC45999 Date: 06/17/99



The Java 2 Standard Edition API Specification (jdk1.3H) reads:
...
public boolean enqueue()

    Adds this reference object to the queue with which it
    is registered, if any.
    Returns:
       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
...

But the following test shows that if we create WeakReference with null
referent object, like this - WeakReference(null, queue), it could not be
enqueued - enqueue() returns false.

The same concerns SoftReference and PhantomReference.

 Test code:
 
  novo51% java -version
  java version "1.3"
  Classic VM (build JDK-1.3-H, green threads, sunwjit)
  novo51% javac test.java
  novo51% java test
  Failed.
  novo51%
 
 ----------------------- test.java ------------------------------------
  import java.io.PrintStream;
  import java.lang.ref.*;
 
  public class test {
 
      public static void main (String args[]) {
           ReferenceQueue queue = new ReferenceQueue();
           WeakReference refWeak = new WeakReference(null, queue);
           if (refWeak.enqueue() == false) {
               System.out.println("Failed.");
               return;
           }
           System.out.println("Passed.");
      }
  }
 -----------------------------------------------------------------------

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