Java编译时无法访问代码错误

Question

我在程序的下一行收到编译时"无法访问的代码"错误:

System.out.println("i ="+ i +",j ="+ j);

public static void main(String[] args) {
    int i = 0, j = 5;
    tp: for (;;) 
    {
        i++;
        for (;;) 
        {
            if (i > --j) {
                break tp;
            }

        }
        System.out.println("i =" + i + ", j = " + j);
    }
}

请帮助我找出确切的原因.提前致谢.

Answer 1

让我们分析一下这段代码:

tp: for (;;)  //<-- similar to while(true)
    {
        i++; //increases i by 1
        for (;;)  //<-- similar to while(true)
        {
            if (i > --j) { //decreases j and compares its value against i
                break tp; //breaks tp, which means breaking the outer for loop
            }
        }
        //while(true) above
        //if break gets executed, it breaks this for loop
        //so this line can never be executed
        System.out.println("i =" + i + ", j = " + j);
    }

最简单的解决方案

移动 System.out.println("i =" + i + ", j = " + j);到外for循环外面.

tp: for (;;)
{
    i++;
    for (;;)
    {
        if (i > --j) {
            break tp;
        }
    }
}
System.out.println("i =" + i + ", j = " + j);