break using label

[Val Lee]

class test{
public static void main(String [] args){
int x = 0;
label2:
while(true){
System.out.println("?" + x);
label:
do {
x++;
System.out.println(x);
switch(x){
case 1: break label;
case 3: break label2;
default: System.out.println(" " + x);
}
}while(x < 0);
}
}
}

out:
?0
1
?1
2
2
?2
3
When x is 1,it get "break label" in switch().
Next,I think it should be perform "x++".
But computer shows it performs "System.out.println("?" + x);".
why?

[Corey McGlone]

From the JLS, §14.14 The break Statement:

A break statement with label Identifier attempts to transfer control to the enclosing labeled statement (�14.7) that has the same Identifier as its label; this statement, which is called the break target, then immediately completes normally.

So, you're right when you say that the target is the do loop. However, that do loop ends abruptly and we continue with the next iteration of the outer loop.
That's why we end up flowing directly into the next iteration of the outer loop.
I hope that helps,
Corey

[Val Lee]

Thx, Corey!
I got it.
"break label" causes do Loop to be abandoned.

[srinivas bolloju]

hi val, x++ will get executed when you have continue there instead of break.,break statement takes you out of the loop,higher up to the next label which is in higher order., i have changed ur code little bit here ... see this...HTH

class test extends Thread{
public static void main(String [] args) throws InterruptedException
{
int x = 0;
//Integer x = new Integer(0);
label2:
while(true)
{
System.out.println("?" + x);
sleep(1000);
label:
do
{
x++;
System.out.println(x);
switch(x)
{
case 1: break label;
case 3: continue label2; //... unending loop
//case 3: break label2;
default: System.out.println(" " + x);
}
}
while(x < 0);
}
}
} 

[Val Lee]

Thx,srinivas!
Good Job!