Eventually occurs java.lang.ArrayIndexOutOfBoundsException [closed]

I made a simple algorithm for a book and there are two possible results. To test these results I have to run the program several times until Math.random () manages the possible numbers and displays the two possible results. The strange thing was that when I was running the code came a point where he presented a message

  

"Exception in thread" main "java.lang.ArrayIndexOutOfBoundsException: 3       at matrixReference3.Hobbits.main (Hobbits.java:25) "

But if I run the program again it returns a result. I would like to understand why this message appears, if it's something dangerous I'm doing in my code.

package matrizReferencia3;

public class Hobbits {
String name;

public static void main(String[] args) {

    Hobbits[] h = new Hobbits[3];
    int z = 0;
    int posicao = 5;

    while(z < 3){ 
        h[z] = new Hobbits();
        z++;
    }

    while (posicao > 3){
    posicao =(int) (Math.random() *10);
    }

    if (posicao == 2){
        h[posicao].name = "sam";
    }
    else{
        h[posicao].name = "frodo";
    }
    System.out.print(h[posicao].name + " is a ");
    System.out.println("good Hobbit name");
}
}