1 /*

     2  * Copyright 1998 Sun Microsystems, Inc.  All Rights Reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  */

    23 

    24 /* @test

    25  * @bug 4181191

    26  * @summary test BigInteger modPow method

    27  */

    28 import java.math.BigInteger;

    29 import java.util.Random;

    30 

    31 public class ModPow {

    32     public static void main(String[] args) {

    33         Random rnd = new Random(1234);

    34 

    35         for (int i=0; i<2000; i++) {

    36             BigInteger m = new BigInteger(800, rnd);

    37             BigInteger base = new BigInteger(16, rnd);

    38             if (rnd.nextInt() % 1 == 0)

    39                 base = base.negate();

    40             BigInteger exp = new BigInteger(8, rnd);

    41 

    42             BigInteger z = base.modPow(exp, m);

    43             BigInteger w = base.pow(exp.intValue()).mod(m);

    44             if (!z.equals(w)){

    45                 System.err.println(base +" ** " + exp + " mod "+ m);

    46                 System.err.println("modPow : " + z);

    47                 System.err.println("pow.mod: " + w);

    48                 throw new RuntimeException("BigInteger modPow failure.");

    49             }

    50         }

    51     }

    52 }