Quelle BitLengthOverflow.java Sprache: JAVA

/*
* Copyright (c) 2013, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* questions.
*/

/*
* @test
* @bug 6910473 8272541
* @summary Test that bitLength() is not negative
* @author Dmitry Nadezhin
*/
import java.math.BigInteger;
import java.util.function.Supplier;

public class BitLengthOverflow {
    private static void test(Supplier<BigInteger> s) {
        try {
            BigInteger x = s.get();
            System.out.println("Surprisingly passed with correct bitLength() " +
                               x.bitLength());
        } catch (ArithmeticException e) {
            // expected
            System.out.println("Overflow reported by ArithmeticException, as expected");
        } catch (OutOfMemoryError e) {
            // possible
            System.err.println("BitLengthOverflow skipped: OutOfMemoryError");
            System.err.println("Run jtreg with -javaoption:-Xmx8g");
        }
    }

    public static void main(String[] args) {
        test(() -> {
            // x = pow(2,Integer.MAX_VALUE)
            BigInteger x = BigInteger.ONE.shiftLeft(Integer.MAX_VALUE);
            if (x.bitLength() != (1L << 31)) {
                throw new RuntimeException("Incorrect bitLength() " +
                                           x.bitLength());
            }
            return x;
        });
        test(() -> {
            BigInteger a = BigInteger.ONE.shiftLeft(1073742825);
            BigInteger b = BigInteger.ONE.shiftLeft(1073742825);
            return a.multiply(b);
        });
    }
}

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