java – Missing return statement within if / for / while

java – Missing return statement within if / for / while

If you put a return statement in the if, while or for statement then it may or may not return a value. If it will not go inside these statements then also that method should return some value (that could be null). To ensure that, compiler will force you to write this return statement which is after if, while or for.

But if you write an if / else block and each one of them is having a return in it then the compiler knows that either the if or else will get executed and the method will return a value. So this time the compiler will not force you.

if(condition)
{
    return;
}
else
{
    return;
}

Thats because the function needs to return a value. Imagine what happens if you execute myMethod() and it doesnt go into if(condition) what would your function return? The compiler needs to know what to return in every possible execution of your function.

Checking Java documentation:

Definition: If a method declaration has a return type then there must
be a return statement at the end of the method. If the return
statement is not there the missing return statement error is thrown.

This error is also thrown if the method does not have a return type
and has not been declared using void (i.e., it was mistakenly
omitted).

You can do this to solve your problem:

public String myMethod()
{
    String result = null;
    if(condition)
    {
        result = x;
    }
    return result;
}

java – Missing return statement within if / for / while

That is illegal syntax. It is not an optional thing for you to return a variable. You must return a variable of the type you specify in your method.

public String myMethod()
{
    if(condition)
    {
        return x;
    }
}

You are effectively saying: I promise any class can use this method (public) and I promise it will always return a String (String).

Then you are saying IF my condition is true I will return x. Well, that is too bad. There isnt any IF in your promise. You promised that myMethod will always return a String.

Even if your condition is always true, the compiler has to assume that there is a possibility of it being false. Therefore you always need to put a return at the end of your non-void method outside of any conditions just in case all of your conditions fail.

public String myMethod()
{
    if(condition)
    {
        return x;
    }
    return ; // Or whatever the default behavior will be if all of your conditions fail to return.
}