public class TestAbs {
    public static void main(String args[]){
        int temp = - 8;
        int out = temp;
        temp = temp >> 31;
        out = out ^ temp;
        out = out - temp;
        System.out.println(out);
    }
}

------解决方案--------------------
Java code
  public static int abs(int num) {
    return num * (1 - ((num >>> 31)<<1));
  }

------解决方案--------------------
1,3,13楼的一样的.

类似的还有:num*(1-((num&0X80000000)>>>30))

略有不同的是:
(num^-(num>>>31))+(num>>>31)