public class tn {
    public class State{
        String s_name;
        int p1;
        int p2;
    }

    public void f(){
        State[] s = new State[10];
        int [] i = new int[10];
        i[0] = 1;                //right
        s[0].p1 = 1;             //error NullPointerException
    }
    public static void main(String[] args) throws Exception {
        tn t = new tn();
        tn.f();
        }

Can anyone help me in 2 comment line, why s[0].p1 = 1 is NullPointerException ???