class GD
{
    public static void main(String args[])
    {
        String s="Hello World",s1="World",s2="Hellz";
        System.out.println(s.indexOf('o'));
        System.out.println(s.indexOf('o',5));
        System.out.println(s.indexOf(s1));
        System.out.println(s.indexOf('z'));
        System.out.println(s.indexOf(s2));
    }
}

godarda@gd:~$ javac GD.java
godarda@gd:~$ java GD
4
7
6
-1
-1
godarda@gd:~$