在Java中，break如何与嵌套循环交互？ [英] In Java, how does break interact with nested loops?

问题描述

我知道 break 语句跳出循环，但是它是跳出嵌套循环还是只跳出它当前的循环？

I know a break statement jumps out of a loop, but does it jump out of nested loops or just the one its currently in?

推荐答案

没有任何装饰， break 将突破最里面的循环。因此，在此代码中：

Without any adornment, break will just break out of the innermost loop. Thus in this code:

while (true) { // A
    while (true) { // B
         break;
    }
}

休息只退出循环 B ，因此代码将永远循环。

the break only exits loop B, so the code will loop forever.

但是，Java有一个功能称为命名中断，您可以在其中命名循环，然后指定要突破的循环。例如：

However, Java has a feature called "named breaks" in which you can name your loops and then specify which one to break out of. For example:

A: while (true) {
    B: while (true) {
         break A;
    }
}

此代码不会永远循环，因为 break 显式离开循环 A 。

This code will not loop forever, because the break explicitly leaves loop A.

幸运的是，这同样的逻辑适用于继续。默认情况下， continue 执行包含 continue 语句的最内层循环的下一次迭代，但它也可用于通过指定循环标签继续执行来跳转到外循环迭代。

Fortunately, this same logic works for continue. By default, continue executes the next iteration of the innermost loop containing the continue statement, but it can also be used to jump to outer loop iterations as well by specifying a label of a loop to continue executing.

在Java以外的语言中，例如C和C ++，这个标记为中断 语句不存在，并且打破多重嵌套循环并不容易。它可以使用 goto 语句来完成，尽管这通常是不受欢迎的。例如，假设您愿意忽略Dijkstra的建议并使用 goto ：

In languages other than Java, for example, C and C++, this "labeled break" statement does not exist and it's not easy to break out of a multiply nested loop. It can be done using the goto statement, though this is usually frowned upon. For example, here's what a nested break might look like in C, assuming you're willing to ignore Dijkstra's advice and use goto:

while (true) {
    while (true) {
        goto done;
    }
}
done:
   // Rest of the code here.

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