Java:label的使用(for迴圈)

標籤：

 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 incremented19                             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 here39     }40 }

輸出

 1 i= 0 2 continue inner 3 i= 1 4 continue inner 5 i= 2 6 continue 7 i= 3 8 break 9 i= 410 continue inner11 i= 512 continue inner13 i= 614 continue inner15 i= 716 continue outer17 i= 818 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.

Java:label的使用(for迴圈)