Why doesn't a Java program compile?

Question

Java

package com.company;
public class lesson {
    public static void main(String[] args) {
        block1:{
            block2:{
                block3:{
                    System.out.println("start");
                    break block2;
                }
                System.out.println("3 break");
            }
            System.out.println("2 break");
        }
        System.out.println("1 break");

    }
}