Java method returning char complaining about not returning char.

Question

Why is this function complaining that it should return a result of type char?

public static char getUserResponseToGuess(int guess){
    Scanner input = new Scanner(System.in);     
    char userResponse = 'x';            
    while((userResponse != 'h' && userResponse != 'l' && userResponse != 'c')){
        System.out.print("Is it" + guess + "? (h/l/c)");        
        userResponse = input.next().charAt(0);
        if (userResponse == 'h' || userResponse == 'l' || userResponse =='c'){
            return userResponse;            
        }
        else{
            System.out.print("Is it" + guess + "? (h/l/c)");
        }
    }
}

Arun P Johny · Accepted Answer · 2015-02-05 04:11:55Z

2

The static analysis done by the compiler does not understand the logic you have used, so based on its analysis all the possible flows does not end up returning a value

When the compiler analysis the code, if the if condition in the code is not satisfied and the loop is exited then the method won't return a value.

public static char getUserResponseToGuess(int guess){
    Scanner input = new Scanner(System.in);     
    char userResponse = 'x';            
    while((userResponse != 'h' && userResponse != 'l' && userResponse != 'c')){
        System.out.print("Is it" + guess + "? (h/l/c)");        
        userResponse = input.next().charAt(0);
        if (userResponse == 'h' || userResponse == 'l' || userResponse =='c'){
            return userResponse;            
        }
        else{
            System.out.print("Is it" + guess + "? (h/l/c)");
        }
    }
    return userResponse;  
}

answered Feb 5, 2015 at 4:11

Arun P Johny

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5 Comments

vanza Over a year ago

If you help the compiler a bit (e.g. by doing a while (true)) it also does not complain.

Vinicius Santana Over a year ago

@vanza ... could you please expand a little on this concept?

vanza Over a year ago

A while (true) loop never finishes, unless you explicitly do it with a return or a break. The compiler sees that the only way out of your loop is a return, so it doesn't complain about the lack of a return value.

Vinicius Santana Over a year ago

Oh wow. I'm kind new to Java. I didn't know a return statement also would get me out of the loop. Good to know. ;)

Vinicius Santana Over a year ago

Now that Im thinking about this is kind what Arun is doing.

Jason · Accepted Answer · 2015-02-05 04:12:06Z

1

What happens when the userResponse is not one of those three characters? It will exit the loop and return what? Every path has to return a char

answered Feb 5, 2015 at 4:12

Jason

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5 Comments

vanza Over a year ago

When it's not one of those characters the code will execute the return statement inside the loop.

vanza Over a year ago

Oops, the opposite. If it's not one of those, it will remain inside the loop until it is, then it executes the return statement.

Jason Over a year ago

The compiler isn't smart enough to walk through all the logic and know that it must return.

vanza Over a year ago

that's true, but that's not what your answer says. Your answer assumes his code is wrong, which is not the case; it's just the compiler that's not smart enough to understand it.

vanza Over a year ago

Well, that's what the question was about: why doesn't it compile. It doesn't compile not because it's logically wrong, but because the compiler isn't smart enough. There is a difference between those two.

Vinicius Santana · Accepted Answer · 2015-02-05 04:26:18Z

0

This worked as it should. Arun P Johny solutions also works.

public static char getUserResponseToGuess(int guess){
    Scanner input = new Scanner(System.in);     
    char userResponse = 'x';            
    System.out.print("Is it " + guess + "? (h/l/c): ");
    while((userResponse != 'h' && userResponse != 'l' && userResponse != 'c')){             
        userResponse = input.next().charAt(0);
        if (userResponse == 'h' || userResponse == 'l' || userResponse =='c'){
            break;                          
        }
        else{
            System.out.print("Is it " + guess + "? (h/l/c): ");
        }
    }
    return userResponse;    
}

answered Feb 5, 2015 at 4:26

Vinicius Santana

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