StackOverflow热帖：Java整数相加溢出怎么办？Java8一步搞定~

public static int addExact(int x, int y) {        int r = x + y;        // HD 2-12 Overflow iff both arguments have the opposite sign of the result        if (((x ^ r) & (y ^ r)) < 0) {            throw new ArithmeticException("integer overflow");        }        return r;}

 public static int subtractExact(int x, int y) {        int r = x - y;        // HD 2-12 Overflow iff the arguments have different signs and        // the sign of the result is different than the sign of x        if (((x ^ y) & (x ^ r)) < 0) {            throw new ArithmeticException("integer overflow");        }        return r;}

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;}

  public static long multiplyExact(long x, long y) {        long r = x * y;        long ax = Math.abs(x);        long ay = Math.abs(y);        if (((ax | ay) >>> 31 != 0)) {            // Some bits greater than 2^31 that might cause overflow            // Check the result using the divide operator            // and check for the special case of Long.MIN_VALUE * -1           if (((y != 0) && (r / y != x)) ||               (x == Long.MIN_VALUE && y == -1)) {                throw new ArithmeticException("long overflow");            }        }        return r;}