Return Type Boolean in Java

Question

I have a question on boolean return types. Check the following code:

Code Sample 1

boolean flag = sampleMethod();

public boolean samplemethod(){
    return false;
}

Code Sample 2

sampleMethod();

public boolean samplemethod(){
    return false; 
}

In the above two examples, the code compiles properly without any compile time or run time exceptions. My doubt is, Java doesn't make it mandatory for the boolean return type to be assigned in the calling program, where for the other data types the program does not work. Can you please explain the reason for this to me?

Answer 1

Java never forces you to assign the return value of a function call. There must be something wrong with your other code (you might post it here, too)

PS: This reminds me of good old Turbo Pascal, where you had to enable the Extended Syntax to get this behaviour.

Answer 2

As @DR says, Java does not force you to assign the result of a method call. A void or non-void method call is valid as a complete statement in Java.

I would surmise that the reasons Java is designed this way include the following:

• Convenience: most experienced developers would find it a nuisance if the result of every non-void method call had to be assigned.

• Tradition: C, C++ and almost no other language force you to do this. (I have vague recollections of some language that did ... but that was long ago.)

• Futility: you cannot stop the developer from assigning the result to a temporary variable and then ignoring it. Or writing a wrapper method that does the same thing.

• Better alternatives: if you want to encourage the developer to pay attention to an error in Java, throw an appropriate checked exception.

Answer 3

javac cannot issue a warning when you forget to assign the result to a variable, but FindBugs can.

@CheckReturnValue(explanation="...")
public boolean samplemethod(){
    return false; 
}

sampleMethod(); // Now generates a warning