如何在Java中打破嵌套循环？

for (Type type : types) {
    for (Type t : types2) {
         if (some condition) {
            return value;
         }
    }
}

最佳且易于实施的方法...

outerloop:
for(int i=0; i<10; i++){
    // here we can break Outer loop by 
    break outerloop;

    innerloop:
    for(int i=0; i<10; i++){
        // here we can break innerloop by 
        break innerloop;
     }
}

boolean broken = false; // declared outside of the loop for efficiency
for (Type type : types) {
    for (Type t : types2) {
        if (some condition) {
            broken = true;
            break;
        }
    }

    if (broken) {
        break;
    }
}

break、continue和label的演示：

Java关键字break和continue有一个默认值，即“最近的循环”，今天，在使用Java几年后，我终于理解了它！

尽管它似乎使用得比较少，但它仍然非常有用。

import org.junit.Test;

/**
 * Created by cui on 17-5-4.
 */

public class BranchLabel {
    @Test
    public void test() {
        System.out.println("testBreak");
        testBreak();

        System.out.println("testBreakLabel");
        testBreakLabel();

        System.out.println("testContinue");
        testContinue();
        System.out.println("testContinueLabel");
        testContinueLabel();
    }

    /**
     testBreak
     a=0,b=0
     a=0,b=1
     a=1,b=0
     a=1,b=1
     a=2,b=0
     a=2,b=1
     a=3,b=0
     a=3,b=1
     a=4,b=0
     a=4,b=1
     */
    public void testBreak() {
        for (int a = 0; a < 5; a++) {
            for (int b = 0; b < 5; b++) {
                if (b == 2) {
                    break;
                }
                System.out.println("a=" + a + ",b=" + b);
            }
        }
    }

    /**
     testContinue
     a=0,b=0
     a=0,b=1
     a=0,b=3
     a=0,b=4
     a=1,b=0
     a=1,b=1
     a=1,b=3
     a=1,b=4
     a=2,b=0
     a=2,b=1
     a=2,b=3
     a=2,b=4
     a=3,b=0
     a=3,b=1
     a=3,b=3
     a=3,b=4
     a=4,b=0
     a=4,b=1
     a=4,b=3
     a=4,b=4
     */
    public void testContinue() {
        for (int a = 0; a < 5; a++) {
            for (int b = 0; b < 5; b++) {
                if (b == 2) {
                    continue;
                }
                System.out.println("a=" + a + ",b=" + b);
            }
        }
    }

    /**
     testBreakLabel
     a=0,b=0,c=0
     a=0,b=0,c=1
     * */
    public void testBreakLabel() {
        anyName:
        for (int a = 0; a < 5; a++) {
            for (int b = 0; b < 5; b++) {
                for (int c = 0; c < 5; c++) {
                    if (c == 2) {
                        break anyName;
                    }
                    System.out.println("a=" + a + ",b=" + b + ",c=" + c);
                }
            }
        }
    }

    /**
     testContinueLabel
     a=0,b=0,c=0
     a=0,b=0,c=1
     a=1,b=0,c=0
     a=1,b=0,c=1
     a=2,b=0,c=0
     a=2,b=0,c=1
     a=3,b=0,c=0
     a=3,b=0,c=1
     a=4,b=0,c=0
     a=4,b=0,c=1
     */
    public void testContinueLabel() {
        anyName:
        for (int a = 0; a < 5; a++) {
            for (int b = 0; b < 5; b++) {
                for (int c = 0; c < 5; c++) {
                    if (c == 2) {
                        continue anyName;
                    }
                    System.out.println("a=" + a + ",b=" + b + ",c=" + c);
                }
            }
        }
    }
}

for (int j = 0; j < 5; j++) //内部循环 应该被替换为 for (int j = 0; j < 5 && !exitloops; j++)。

在这种情况下，如果条件为 True，则应该完全退出嵌套循环。但是，如果我们仅将 exitloops 应用于上层的 loop。

 for (int i = 0; i < 5 && !exitloops; i++) //upper loop

boolean exitloops = false;
for (int i = 0; i < 5 && !exitloops; i++) { //here should exitloops as a Conditional Statement to get out from the loops if exitloops become true. 
    for (int j = 0; j < 5 && !exitloops; j++) { //here should also use exitloops as a Conditional Statement. 
        if (i * j > 6) {
            exitloops = true;
            System.out.println("Inner loop still Continues For i * j is => "+i*j);
            break;
        }
        System.out.println(i*j);
    }
}

Java不像C++一样有goto功能。但是，goto在Java中仍然是一个保留关键字。他们可能会在将来实现它。对于你的问题，答案是Java中有一种叫做标签的东西，你可以在其上应用continue和break语句。下面是代码：

public static void main(String ...args) {
    outerLoop: for(int i=0;i<10;i++) {
    for(int j=10;j>0;j--) {
        System.out.println(i+" "+j);
        if(i==j) {
            System.out.println("Condition Fulfilled");
            break outerLoop;
        }
    }
    }
    System.out.println("Got out of the outer loop");
}

像 @1800 INFORMATION 的建议一样，将打破内部循环的条件作为外部循环的条件:

boolean hasAccess = false;
for (int i = 0; i < x && hasAccess == false; i++){
    for (int j = 0; j < y; j++){
        if (condition == true){
            hasAccess = true;
            break;
        }
    }
}

如果这是一个新的实现，您可以尝试将逻辑重写为if-else_if-else语句。

while(keep_going) {

    if(keep_going && condition_one_holds) {
        // Code
    }
    if(keep_going && condition_two_holds) {
        // Code
    }
    if(keep_going && condition_three_holds) {
        // Code
    }
    if(keep_going && something_goes_really_bad) {
        keep_going=false;
    }
    if(keep_going && condition_four_holds) {
        // Code
    }
    if(keep_going && condition_five_holds) {
        // Code
    }
}

something_bad_has_happened = false;
while(something is true && !something_bad_has_happened){
    // Code, things happen
    while(something else && !something_bad_has_happened){
        // Lots of code, things happens
        if(something happened){
            -> Then control should be returned ->
            something_bad_has_happened=true;
            continue;
        }
    }
    if(something_bad_has_happened) { // The things below will not be executed
        continue;
    }

    // Other things may happen here as well, but they will not be executed
    //  once control is returned from the inner cycle.
}

看这里！虽然简单的break语句无法满足需求，但可以使用continue语句来实现。

如果你只是想在Java中移植逻辑并使代码正常工作，可以尝试使用标签。

你只需使用标签来中断内部循环

public class Test {
public static void main(String[] args) {
    outerloop:
for (int i=0; i < 5; i++) {
  for (int j=0; j < 5; j++) {
    if (i * j > 6) {
      System.out.println("Breaking");
      break outerloop;
    }
    System.out.println(i + " " + j);
  }
}
System.out.println("Done");
}
}

1. set a local variable to false

2. set that variable true in the first loop, when you want to break

3. then you can check in the outer loop, that whether the condition is set then break from the outer loop as well.

   boolean isBreakNeeded = false;
   for (int i = 0; i < some.length; i++) {
       for (int j = 0; j < some.lengthasWell; j++) {
           //want to set variable if (){
           isBreakNeeded = true;
           break;
       }
   
       if (isBreakNeeded) {
           break; //will make you break from the outer loop as well
       }
   }