String s1 = "cat";
        String s2 = "car";
        String s3 = "catch";

        s1.compareTo(s2) is > 0  s1 comes after s2
        s1.compareTo(s3) is < 0  s1 comes before s3
        s1.compareTo("cat") is 0    s1 is equal to "cat"
        s1.equals(s2) is false
        s1.equals(s1) is true
        s1.equals("cat") is true