Reverse a sentence in Java [closed]

The question for homework is the program should print the String in reverse word by word.
Your `String' should be assigned the value “pay no attention to that man behind the curtain” and should be printed as the sample output.

Getting errors compiling and been at this for 3 hours - lost!!

I must use the charAt method, the substring method and an if statement:

curtain
the
behind
man
that
to
attention
no
pay

---

public class backwards
{
    public static void main(String args[])
    {
        String s1 = new String("pay no attention to that man behind the curtain");

        /*int pos = s1.indexOf(' ');
        while(s1.length() >  0)
        {
            if(pos == -1)
            {
                System.out.println(s1);
                s1 = "";

            }
            else
            {
                System.out.println(s1.substring(0,pos));
                s1 = s1.substring(pos+1);
                pos = s1.indexOf(' ');
            }

        }*/
        int pos = 0;
        for(int i = s1.length()-1 ; i >= 0; i--)
        {
        //  System.out.println("Pos: " + pos);
            if(s1.charAt(i) == ' ')
            {
                System.out.println(s1.substring(i+1));
                s1 = s1.substring(0,i);
            }
            else if(i == 0)
            {
                System.out.println(s1);
                s1 = "";
            }
        }
    }
}