Saturday, November 19, 2011

difference between return; and return (xx); in Java

java return keyword is one of the most frequently used keyword in java and also one of the concept, which most programmers say they are well aware of. But, I still meet programmers who say that they are little confused when they come down to return statement. Especially with respect to the method which has void as their return type. So, this post would help you in clearing those doubts and help you understand the clear picture of it... in the most simplest way.

We all know that Java return keyword is used to return the control back to calling method with a certain data-type which was promised during the method declaration. As many wanted to know if we can use just the return keyword(like this: return;) but not return any value(like this: return obj;), then I have to say yes to that. Se the below java programs which will help you understanding the difference better,

public class ReturnTypes {
    public static void main(String args[]){
    public static int
        return 1;

    private static void
functionVoid() {
        // return;  // This line if UnCommented, would result in Compilation error

If you see in the method functionType() the return keyword is used to return an primitive int value, which is quiet normal and know to almost every java programmer.

But, If you see the method functionVoid() it in fact uses the controversial return keyword(just "return;") which doesn't return anything at-all. Yes this is absolutely valid to use it that way... Ahaaaa hold on, I am not yet done completely... and now imagine if you can use the same return type outside the scope of if statement, as It's already available in program but commented out... That will certainly thorough you an compilation error.

Now why so.. There is nothing wrong with the syntax of return; statement but the error is something different as the compiler is just complaining about "Unreachable Code"... 

By now you know that we can use both of these conventions and are very much valid. But you can ask yourself a question on why actually java needs a return; statement in the first, when we already know that the method is not meant to return any thing back to the calling function as we have declared it void...??

The answer is, you can treat return keyword as a form of goto statement. As it will directly move the control to the line where the method is called. And if you want to accomplish that in an void method then what other option you have to do that other than return; statement. 

Hope that this post helped you understanding the difference better. Please drop your comments on this post for question or answers or suggestions or discussions...

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