Name: jl125535 Date: 03/20/2002


FULL PRODUCT VERSION :
F:\>java -version
java version "1.3.1"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1-b24)
Java HotSpot(TM) Client VM (build 1.3.1-b24, mixed mode)

FULL OPERATING SYSTEM VERSION : win2k pro
Verified on Solaris 8 with both JDK 1.3.1 and JDK 1.4.

A DESCRIPTION OF THE PROBLEM :
java.math.BigInteger.isProbablePrime(Integer.MAX_VALUE) returns true for even numbers from 4 to 1*10^6 (and probably beyond).

Note that BigInteger.isProbablePrime(Integer.MAX_VALUE - 1) correctly returns false for those same values.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
run the test case

This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.math.BigInteger;

public class Test
{
    public static void main(String[] args)
    {
        BigInteger onemill = new BigInteger(1000000 + "");
        BigInteger two = new BigInteger(2 + "");
        BigInteger test = new BigInteger(0 + "");
        while (true)
        {
            if (test.isProbablePrime(Integer.MAX_VALUE))
            {
                // This line should never appear (except for 2)
                
                //System.out.println(test
                // + ".isProbablePrime(MAX_VALUE) = false");
            }
            else
            {
                // This line should always appear (exepct for 2)
                //this will only be printed if sProbablePrime is correct
                //except test value of 2
                System.out.println(test
                                   + ".isProbablePrime(MAX_VALUE) = false");
             }
            test = test.add(two);
            if (test.equals(onemill))
            {
                System.out.println("If only this line appeared, the test "
                                   + "failed.");
                break;
            }
        }
    }
}
---------- END SOURCE ----------

CUSTOMER WORKAROUND :
don't use Integer.MAX_VALUE for the certainty
(Review ID: 144259)
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