Java:label的使用，for循环

 1 package java_test;
 2 
 3 public class LabeledFor {
 4 
 5     public static void main(String[]args){
 6         int i=0;
 7         outer: //Cannot have statement here
 8             for(;true;){
 9                 inner:
10                     for(;i<10;i++){
11                         System.out.println("i= "+i);
12                         if(i==2){
13                             System.out.println("continue");
14                             continue;
15                         }
16                         if(i==3){
17                             System.out.println("break");
18                             i++; //Otherwise i never gets incremented
19                             break;
20                         }
21                         if(i==7){
22                             System.out.println("continue outer");
23                             i++;
24                             continue outer;
25                         }
26                         if(i==8){
27                             System.out.println("break outer");
28                             break outer;
29                         }
30                         for(int k=0;k<5;k++){
31                             if(k==3){
32                                 System.out.println("continue inner");
33                                 continue inner;
34                             }
35                         }
36                     }
37             }
38             //Cannot break or continue to labels here
39     }
40 }

输出

 1 i= 0
 2 continue inner
 3 i= 1
 4 continue inner
 5 i= 2
 6 continue
 7 i= 3
 8 break
 9 i= 4
10 continue inner
11 i= 5
12 continue inner
13 i= 6
14 continue inner
15 i= 7
16 continue outer
17 i= 8
18 break outer

用法：

 1 label1:
 2     outer-iteration{
 3     inner-iteration{
 4         //...
 5         break;//(1)
 6         //...
 7         continue;//(2)
 8         //...
 9         continue label1;//(3)
10         //...
11         break label1;//(4)
12     }
13 }

In (1),the break breaks out of the inner iteration and you end up in the out iteration.

in(2), the continue moves back to the beginning of the inner iteration.

But in (3),the continue label1 breaks out of the inner iteration and the outer iteration,all the way back to label1. Then it does in fact continue the iteration,but starting at the outer iteration.

In(4),the break label1 also breaks all the way out to label1,but it does not reenter the iteration.It actually does break out of both iterations.