New to Java

I am practicing this program and its giving me error:

error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException:3 at Testarray.main

Code:

class Testarray

{

String name;

public static void main (String [] args)

{

Testarray[] h= new Testarray[3];

int z=-0;

while (z<4)

{

z=z+1;

h[z] = new Testarray();

h[z].name="abc";

if (z==1) {

h[z].name="def";

}

if (z==2){

h[z].name="xyz";

}

System.out.println(h[z].name + " is a");

System.out.println("good Testarray name");

}

}

}

thanks
Cindy