AbsTest.java

public class AbsTest {
    public static int absSpec(int x) {
        return x < 0 ? -x : x;
    }
    
    public static int absImpl(int x) {
        int signbits = x >> 31;
        int xor = x ^ signbits;
        return xor + (signbits & 0x01);
    }
    
    public static void main(String []args) {
        for(int i = -3; i < 5; i++)
            System.out.printf("abs(%d): %s\n", 
            i, absImpl(i) == absSpec(i) ? "passed" : "failed");
    }
}