continue and break can change the execution flow of the loop, but in multiple loops, these two statements cannot directly jump from the inner loop to the outer loop. In C language, multiple loop jumps can be achieved through goto statements, but using goto statements in non-loop structures will make the program structure disordered and make the readability worse. Therefore, Java invented a labeled continue and break statement. In fact, it is a restricted goto statement specially used for loops.
Normally, the continue (or break) statement we use does not have a label. In this case, the continue (or break) statement is executed in the current loop by default. A labeled loop actually gives the loop a name. When using the "continue (or break) + label" statement, it actually executes the continue (or break) statement in the loop where the label is located.
Now we use three examples to illustrate labeled loops.
1. Unlabeled double loop
package javaleanning; public class LableTest { public static void main(String[] args) { for(int i = 0; i < 10; i++){ for(int j = 0; j < 10; j++){ System.out.print("("+i+","+j+") "); } System.out.println(); } } }
Running result
(0,0) (0,1) (0,2) (0,3) (0,4) (0, 5) (0,6) (0,7) (0,8) (0,9)
(1,0) (1,1) (1,2) (1,3) (1,4) ( 1,5) (1,6) (1,7) (1,8) (1,9)
(2,0) (2,1) (2,2) (2,3) (2,4 ) (2,5) (2,6) (2,7) (2,8) (2,9)
(3,0) (3,1) (3,2) (3,3) (3 ,4) (3,5) (3,6) (3,7) (3,8) (3,9)
(4,0) (4,1) (4,2) (4,3) (4,4) (4,5) (4,6) (4,7) (4,8) (4,9)
(5,0) (5,1) (5,2) (5, 3) (5,4) (5,5) (5,6) (5,7) (5,8) (5,9)
(6,0) (6,1) (6,2) ( 6,3) (6,4) (6,5) (6,6) (6,7) (6,8) (6,9)
(7,0) (7,1) (7,2 ) (7,3) (7,4) (7,5) (7,6) (7,7) (7,8) (7,9)
(8,0) (8,1) (8 ,2) (8,3) (8,4) (8,5) (8,6) (8,7) (8,8) (8,9)
(9,0) (9,1) (9,2) (9,3) (9,4) (9,5) (9,6) (9,7) (9,8) (9,9)
2. Labeled double loop , the "break+label" statement
is a double for loop in this example. We added a label to the beginning of the outer loop (that is, giving the outer loop a name) "outerCycle", and the inner loop When using "break outerCycle" in a loop, it is equivalent to using the break statement directly in the outerCycle cycle.
package javaleanning; public class LableTest { public static void main(String[] args) { outerCycle: for(int i = 0; i < 10; i++){ for(int j = 0; j < 10; j++){ if(j == 5){ break outerCycle; } System.out.print("("+i+","+j+") "); } System.out.println(); } } }
Running result
(0,0) (0,1) (0,2) (0,3) (0,4)
3. Labeled double loop, "continue+label "The statement
in this example is a double for loop. We added a label to the beginning of the outer loop (that is, giving the outer loop a name) "outerCycle", and used "continue" in the inner loop. outerCycle", it is equivalent to using the continue statement directly in the outerCycle cycle.
package javaleanning; public class LableTest { public static void main(String[] args) { outerCycle: for(int i = 0; i < 10; i++){ for(int j = 0; j < 10; j++){ if(j == 5){ continue outerCycle; } System.out.print("("+i+","+j+") "); } System.out.println(); } } }
Run results
(0,0) (0,1) (0,2) (0,3) (0,4) (1,0) (1,1) (1,2 ) (1,3) (1,4) (2,0) (2,1) (2,2) (2,3) (2,4) (3,0) (3,1) (3,2 ) (3,3) (3,4) (4,0) (4,1) (4,2) (4,3) (4,4) (5,0) (5,1) (5,2 ) (5,3) (5,4) (6,0) (6,1) (6,2) (6,3) (6,4) (7,0) (7,1) (7,2 ) (7,3) (7,4) (8,0) (8,1) (8,2) (8,3) (8,4) (9,0) (9,1) (9,2 ) (9,3) (9,4)
Note: The actual running results are all displayed on one line (that is, no line break statement is executed). The current display results are only for typesetting reasons
More in-depth analysis of Java For related articles on the role of tags in loops, please pay attention to the PHP Chinese website!