java语言——如何判断整数溢出-白红宇

java语言——如何判断整数溢出

阅读量：339 次

发布时间：2019-03-04

本文共 1477 字，大约阅读时间需要 4 分钟。

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public static int addExact(int x, int y) {    int r = x + y;    // ???????    boolean overflow = ( (x ^ r) > 0 ) != ( (y ^ r) > 0 );    if (overflow) {        throw new ArithmeticException("integer overflow");    }    return r;}

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public static int subtractExact(int x, int y) {    int r = x - y;    // ???????    boolean overflow = ( (x ^ r) > 0 ) != ( (y ^ r) > 0 );    if (overflow) {        throw new ArithmeticException("integer overflow");    }    return r;}

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public static int multiplyExact(int x, int y) {    long r = (long)x * (long)y;    if ( (int)r != r ) {        throw new ArithmeticException("integer overflow");    }    return (int)r;}

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public static long multiplyExact(long x, long y) {    long r = x * y;    // ???????    if ( (x == 0 || y == 0) ) {        return r;    }    // ???????    long ax = Math.abs(x);    long ay = Math.abs(y);    if ( (ax > Integer.MAX_VALUE / ay) || (ay > Integer.MAX_VALUE / ax) ) {        // ????        long temp = r / y;        if ( (y != 0) && (temp != x) ) {            throw new ArithmeticException("long overflow");        }        // ??????        if (x == Long.MIN_VALUE && y == -1) {            throw new ArithmeticException("long overflow");        }    }    return r;}