Piedra, Papel o Tijeras en JAVA

import java.util.Scanner;

public class ppt {
public static void main(String[] ar) {
Scanner teclado=new Scanner(System.in);
String usu,cpu;
String[] opc={"piedra","papel","tijeras"};

        System.out.println("Elige:");
usu=teclado.next();
  int num = (int) Math.floor(Math.random()*(2-0+1)+0);  cpu = opc[num];
switch (usu) {
case "piedra":
switch (cpu){
case "piedra":
System.out.println("CPU elije PIEDRA. EMPATE");
break;
case "papel":
System.out.println("CPU elije PAPEL. Gana CPU");
break;
case "tijeras":
System.out.println("CPU elije TIJERAS. Ganas TU");
break;
}
       break;
   case "papel":
switch (cpu){
case "piedra":
System.out.println("CPU elije PIEDRA. Ganas TU");
break;
case "papel":
System.out.println("CPU elije PAPEL. EMPATE");
break;
case "tijeras":
System.out.println("CPU elije TIJERAS. Gana CPU");
break;
}
       break;
   case "tijeras":
switch (cpu){
case "piedra":
System.out.println("CPU elije PIEDRA. Gana CPU");
break;
case "papel":
System.out.println("CPU elije PAPEL. Ganas TU");
break;
case "tijeras":
System.out.println("CPU elije TIJERAS. EMPATE");
break;
}
       break;
   default:
       System.out.println("Incorrecto");
       break;
}
}
}