Name: ddT132432 Date: 09/17/2001


java version "1.4.0-beta2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta2-b77)
Java HotSpot(TM) Client VM (build 1.4.0-beta2-b77, mixed mode)


The general contract of Map.equals() does not permit throwing a
NullPointerException; it simply permits returning true or false. However, this
simple program demonstrates that AbstractMap simply delegates to Map.get(),
which can throw a NullPointerException in the case of Hashtable, where null keys
are not permitted. Therefore, AbstractMap is flawed, and needs to trap any
exceptions and return false in such a case.

import java.util.*;
class Foo {
  public static void main(String[] args) {
    Map m = new HashMap();
    m.put(null, "");
    Map h = new Hashtable();
    h.put("", "");
    m.equals(h);
  }
}

$ java Foo
Exception in thread "main" java.lang.NullPointerException
        at java.util.Hashtable.get(Hashtable.java:321)
        at java.util.AbstractMap.equals(AbstractMap.java:519)
        at Foo.main(Foo.java:8)
(Review ID: 132020)
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