Android Long Overflow Check mulAndCheck(long a, long b)

Description

Multiply two long integers, checking for overflow.

License

Apache License

Parameter

Parameter	Description
a	Factor.
b	Factor.

Exception

Parameter	Description
MathArithmeticException	if the result can not be representedas a long.

Return

the product a * b .

Declaration

public static long mulAndCheck(long a, long b)
        throws MathArithmeticException 

Method Source Code

/*// w ww.  ja  v  a 2s  .c  om
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.math.BigInteger;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.commons.math3.exception.MathArithmeticException;
import org.apache.commons.math3.exception.NotPositiveException;
import org.apache.commons.math3.exception.NumberIsTooLargeException;
import org.apache.commons.math3.exception.util.Localizable;
import org.apache.commons.math3.exception.util.LocalizedFormats;

public class Main{
    /**
     * Multiply two integers, checking for overflow.
     *
     * @param x Factor.
     * @param y Factor.
     * @return the product {@code x * y}.
     * @throws MathArithmeticException if the result can not be
     * represented as an {@code int}.
     * @since 1.1
     */
    public static int mulAndCheck(int x, int y)
            throws MathArithmeticException {
        long m = ((long) x) * ((long) y);
        if (m < Integer.MIN_VALUE || m > Integer.MAX_VALUE) {
            throw new MathArithmeticException();
        }
        return (int) m;
    }
    /**
     * Multiply two long integers, checking for overflow.
     *
     * @param a Factor.
     * @param b Factor.
     * @return the product {@code a * b}.
     * @throws MathArithmeticException if the result can not be represented
     * as a {@code long}.
     * @since 1.2
     */
    public static long mulAndCheck(long a, long b)
            throws MathArithmeticException {
        long ret;
        if (a > b) {
            // use symmetry to reduce boundary cases
            ret = mulAndCheck(b, a);
        } else {
            if (a < 0) {
                if (b < 0) {
                    // check for positive overflow with negative a, negative b
                    if (a >= Long.MAX_VALUE / b) {
                        ret = a * b;
                    } else {
                        throw new MathArithmeticException();
                    }
                } else if (b > 0) {
                    // check for negative overflow with negative a, positive b
                    if (Long.MIN_VALUE / b <= a) {
                        ret = a * b;
                    } else {
                        throw new MathArithmeticException();

                    }
                } else {
                    // assert b == 0
                    ret = 0;
                }
            } else if (a > 0) {
                // assert a > 0
                // assert b > 0

                // check for positive overflow with positive a, positive b
                if (a <= Long.MAX_VALUE / b) {
                    ret = a * b;
                } else {
                    throw new MathArithmeticException();
                }
            } else {
                // assert a == 0
                ret = 0;
            }
        }
        return ret;
    }
}

Related

1. addAndCheck(long a, long b)
2. addAndCheck(long a, long b, Localizable pattern)
3. subAndCheck(long a, long b)