java - 无法理解Core java for循环和switch case语句逻辑

Question

这是我的问题。下面的代码中 {j++;} 的用途是什么？为什么如果我注释 {j++;} 虽然 j = 0 为什么它不进入 case(0) 内部。没有 {j++;} 行的答案输出是 0。为什么不是 1。

class Strings {
    public static void main(String args[]) {
        int i, j = 0;
        for (i = 10; i < 0; i--) {
            j++;
        }
        switch (j) {
            case (0):
                j = j + 1;
            case (1):
                j = j + 2;
                break;
            case (2):
                j = j + 3;
                break;
            case (10):
                j = j + 10;
                break;
            default:
                break;
        }

        System.out.println(j);
    }
}

Answer 1

因为没有break语句。它会转到0个case和1个case。将System.out.println()放在cases内部，你可以自己找到发生的事情

initially j is zero . because you for loop not run as condition is false (10<1) is false.

case (0) : //goes inside of this case because j==0;
j=j+1;

//now j is 1 and goes to  case 1

case (1):  //goes to this case too
j = j + 2; //now j is 3
break;     //exit from here