Name: auR10023 Date: 08/14/2001



java.util.HashMap.containsKey doesn`t work with null keys.
The javadoc for this method says nothing about the difference between
null and non-null keys.

javadoc for HashMap:

...
containsKey

public boolean containsKey(Object key)

     Returns true if this map contains a mapping for the specified key.

     Specified by:
          containsKey in interface Map
     Overrides:
          containsKey in class AbstractMap
     Parameters:
          key - The key whose presence in this map is to be tested
     Returns:
          true if this map contains a mapping for the specified key.
...

But this method returns false for null key contained in the HashMap.

Here is the example:

---------------t.java---------------


import java.util.*;

class t {
    public static void main(String args[]) {
        HashMap map = new HashMap();
        
        map.put(null, null);
        map.put("dd", "dd");
        System.out.println( map.containsKey(null));
    }
}

#java -version
java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0-C)
Java HotSpot(TM) Client VM (build 1.3.0-C, interpreted mode)

#java t
true

#java -version
java version "1.4.0-beta_refresh"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta_refresh-b75)
Java HotSpot(TM) Client VM (build 1.4.0-beta_refresh-b75, mixed mode)

#java t
false

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