java - Java 中的冒号有什么作用？

Question

public void go(){
    String o = "";
    z:
    for (int x = 0; x<3; x++) {
        for (int y = 0; y<2;y++) {
            if (x==1) 
                break;
            if (x==2 && y==1)
                break z;
            o = o + x+y;
        }
    }

    System.out.println(o);
}

Answer 1

它是label对于导演break (或 directed continue )。请参阅下面添加的评论:

public void go(){
    String o = "";
    z:                       // <=== Labels the loop that follows
    for (int x = 0; x<3; x++) {
        for (int y = 0; y<2;y++) {
            if (x==1) 
                break;       // <=== Not directed, only breaks the inner loop
            if (x==2 && y==1)
                break z;     // <=== Directed break, breaks the loop labelled with `z`
            o = o + x+y;
        }
    }

    System.out.println(o);
}