What does this line do?

[Mat Cauthon]

I got this out of my text book for my programming principles class. This code shows name overloading in Java. The line in question is in bold.

class A{
 
A A(A A)
{
        [bold]A:[/bold]
for(; ;) 
{
if(A.A(A) == A) break; 
}
return A;
}
}

[ October 01, 2006: Message edited by: Marilyn de Queiroz ]

[Keith Lynn]

That is a label. You can find the specification for it in Section 14.7 of the Java Language Specification, Third Edition.
[ October 01, 2006: Message edited by: Keith Lynn ]

[Pratibha Malhotra]

Yes, it is a way to label a statement. Main purpose behind same is to to provide a mark to a particular line of code.

It is primarily used in Loops for decision making for flow of control and is useful with break and continue operations

outer:
for( i=0; i<10; i++ ){
for( j=10; j>0; j--){
if( j == 5 ) {
break outer; // exit entire loop-labeled as outer
}
}
}

HTH,

[Jesper de Jong]

Ok, so now that you've learned what a label is, please forget about it and don't use it in your own code ever again...

You don't need this construction, it makes code hard to read and follow. A label and a break statement to jump to the label are more or less like a "goto" statement, the statement that quickly makes programs a messy jumble (spaghetti code).