Name: gm110360 Date: 02/27/2004


FULL PRODUCT VERSION :
java version "1.5.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta-b32c)
Java HotSpot(TM) Client VM (build 1.5.0-beta-b32c, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP

A DESCRIPTION OF THE PROBLEM :
The internal hash function in IdentityHashMap only returns even numbers. Only 1/2 of the internal table is actually used.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Should return a fairly even distribution for the table.
ACTUAL -
All hash results were even.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
    public static void main(String[] args) {
        for (; ; ) {
            System.out.println(hash(new Object(), 64));
        }
    }

    private static int hash(Object x, int length) {
        int h = System.identityHashCode(x);
        // Multiply by -127, and left-shift to use least bit as part of hash
        return ((h << 1) - (h << 8)) & (length - 1);
    }
---------- END SOURCE ----------
(Incident Review ID: 240630)
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