java 可以对外循环使用 break 吗？

Possible to use break for outer loop?

提问by 3D-kreativ

If I use breaklike the code below, then the loop within rowwon't iterate the rest if there is a match in the beginning, but what about the colloop?

如果我break像下面的代码一样使用，那么row如果开头有匹配项，则其中的循环将不会迭代其余部分，但是col循环呢？

Would it still iterate between 0 and 7? Is there a way to use breakthere as well?

它还会在 0 和 7 之间迭代吗？有没有办法在break那里使用？

for (int col = 0; col < 8; col ++)
    for (int row = 0; row < 8; row ++)
        if (check something)
        {
            //Then do this;
            break;
        }

回答by Jon Skeet

One option is to use a condition flag. You could then eitherbreak in the outer loop as well, or just use it as an extra condition within the forloops:

一种选择是使用条件标志。然后，您也可以中断外部循环，或者仅将其用作for循环中的额外条件：

bool keepGoing = true;

for (int col = 0; col < 8 && keepGoing; col++)
{
    for (int row = 0; row < 8 && keepGoing; row++)
    {
        if (something)
        {
             // Do whatever
             keepGoing = false;
        }
    }
}

In Java you can specify a label to break to though. (I didn't see that this question was tagged Java as well as C#.)

在 Java 中，您可以指定要中断的标签。（我没有看到这个问题被标记为 Java 和 C#。）

outerLoop:
for (...)
{
    for (...)
    {
        if (...)
        {
            break outerLoop;
        }
    }
}

EDIT: As noted in comments, in C# you coulduse a label and goto:

编辑：如评论中所述，在 C# 中，您可以使用标签和goto：

for (...)
{
    for (...)
    {
        if (...)
        {
            goto endOfLoop;
        }
    }
}
endOfLoop:
// Other code

I'd reallyrecommend that you don't take either of these approaches though.

不过，我真的建议您不要采用这两种方法中的任何一种。

In both languages it would usually be best to simply turn both loops into a single method - then you can just return from the method:

在这两种语言中，通常最好将两个循环简单地转换为一个方法 - 然后您可以从该方法返回：

public void doSomethingToFirstOccurrence()
{
    for (...)
    {
        for (...)
        {
            if (...)
            {
                return;
            }
        }
    }
}

回答by anshulkatta

Yes, it is possible by using a breaklabel:

是的，可以使用break标签：

package others;

public class A {

    public static void main(String[] args) {
        outer: for(int col = 0; col < 8; col ++)
        {
            for (int row = 0; row < 8; row ++)
            {
                if (col == 4)
                {
                    System.out.println("hi");
                    break outer;
                }
            }
        }
    }
}

回答by Subhrajyoti Majumder

You can put logic like this:

你可以像这样放置逻辑：

boolean condition = false;

for (int col = 0; col < 8; col ++)
    for (int row = 0; row < 8; row ++)
        if (check something) {
            // Then do this:
            condition = true; // Break condition for outer loop
            break;
        }
     }
     if (condition)
         break;
 }

回答by Fabio Marcolini

It doesn't exit the col loop.

它不会退出 col 循环。

Instead, you can wrap all in a function and use return;to exit immediately from the loop

相反，您可以将所有内容包装在一个函数中并用于return;立即退出循环

private Xy Loop( /* Parameters */)
    for (int col = 0; col < 8; col ++)
        for (int row = 0; row < 8; row ++)
            if (check something) {
                // Then do this;
                return something; //Or just return;
            }
        }
    }
}

回答by Marco Forberg

breakonly breaks the loop that is directly around it. You could use a flag to control the outer loop:

break只会打破直接围绕它的循环。您可以使用标志来控制外循环：

boolean continueOuterLoop = true;

for(int col = 0; continueOuterLoop && col < 8; col ++) {
    for(int row = 0; row < 8; row ++) {
        if(check something) {
            //Then do this;
            continueOuterLoop = false;
            break;
        }
    }
}

回答by Michael 'Maik' Ardan

nameHere:
for (yourForLoop) {
    for (anotherLoop) {
        if(condition) {
            break nameHere;
        }
    }
}

回答by anddevmanu

I think you should use a tag or a label, like "outerLoop". This works in Java:

我认为您应该使用标签或标签，例如“outerLoop”。这适用于 Java：

outerLoop:
    for (int col = 0; col < 8; col ++)
        for (int row = 0; row < 8; row ++)
            if (check something)
            {
                //Then do this;
                break outerLoop;
            }

回答by Aristos

One more alternative to the other answers is to set your counters to the maximum, to stop the loops.

其他答案的另一种替代方法是将计数器设置为最大值，以停止循环。

for (int col = 0; col < 8; col ++)
    for (int row = 0; row < 8; row ++)
        if (check something)
        {
            // Use the col and row here.

            // Now we go for a totally break of all loops.
            // To stop the loops you can set that to the maximum
            // of your loop test.
            row = 8;
            col = 8;
        }

The advantage to that trick is that you do not add any additional checking code to the full loop and that makes it a lot faster.

该技巧的优点是您无需向完整循环添加任何额外的检查代码，从而使其速度更快。

回答by Peter Olson

In Java you can use a break label

在 Java 中，您可以使用 break label

outer: 
for (int col = 0; col < 8; col ++)
    for (int row = 0; row < 8; row ++)
        if (check something)
        {
            break outer;
        }
    }
}

And, since nobody else has mentioned it yet, in C# you can use goto label

而且，由于还没有其他人提到它，在 C# 中你可以使用 goto label

for (int col = 0; col < 8; col ++)
    for (int row = 0; row < 8; row ++)
        if (check something)
        {
            goto outside;
        }
    }
}
outside:

回答by Ramesh

    Loop1: 
    for (int col = 0; col < 8; col ++)
    {
        for (int row = 0; row < 8; row ++)
        {
            if (condition)
            {
                break Loop1;
            }
        }
    }

This could do what you need...

这可以做你需要的......