Java: Error-"This method must return a result of type Boolean"

[RockSolid1106]

So I am trying to make a very simple program, which would sift through an array to check if it contains my specified word. If the word is found in the array, a true(boolean) value will be returned, else false. So I have created a method for that and it throws an error:

This method must return a result of type Boolean

My code:

public class pg202Q7 {
    public static void main(String args[]){
        String x[]={"hello", "how", "are", "you"};
        System.out.println(inarray(x, "are"));
        }

    public static Boolean inarray(String array[], String needle){
        int i=0;

        for(;i<array.length; i++){
            if(array[i]==needle){
                return true;
            }
            else{
                return false;
            }
            }
        }
        }
    

 

And here's the full error:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
        This method must return a result of type Boolean

        at pg202Q7.inarray(pg202Q7.java:7)
        at pg202Q7.main(pg202Q7.java:4)

 

And this shows the line numbers to make it easy to understand:

Spoiler

Thanks!

Edited July 16, 2021 by RockSolid1106

[Trinopoty]

Basically what it says, you need to return a value at the end of your method. In this particular case, move the "return false" statement to the end of the method.

Java is not C, you don't need to declare all your variables at the top of the method. You can declare and use a variable anywhere in your method, it's like some arcane magic.

Also, use proper formatting to make the life of everyone involved a bit easier (including yours).

[minibois]

A function with a return type (in this your function "inarray()") must always be able to return a value (of type boolean, in this case).

 

Dissecting your function, if there is data in the array, the for-loop will run and will spit out a return true or return false.

What if there is no data in the array though? That would mean the function doesn't ever reach the 'return true;' or 'return false;' parts of the code.

That is what the code is complaining about.

 

You would fix that by simply doing this:

public static Boolean inarray(String array[], String needle){
        for(int i = 0; i < array.length; i++){
            if(array[i]==needle){
                return true;
            }
        }
	return false;
}

 

I have applied a few changes to your code.

'Boolean p' is set to false. By default, you want to assume the needle-word is not contained in the array, unless proven otherwise. You first set it to false, then loop through the array and if the code finds out the needle-word is there, then it decides to set the boolean to true.

 

I removed the else.

By saying "return false", you end a function. What your current function did, is it looks at the first word in the array and it either sees it's the needle-word or not and returns a true or false value (in your example false, as it compares 'hello' to 'are') and that's it. I assumed you wanted the function to look at the entire array?

With the above changes, it now looks at every word in the array and if one (or multiple) word(s) match the needle-word, it returns true. If it doesn't find the needle-word (doesn't enter the if statement) it will simply loop through the entire array, reach 'return p;' (which would be false, like declared above) and that's it.

 

Now with the above there will always be a return path.

Either it finds the needle-word in the array and returns true, or it doesn't and it returns false.

 

TL;DR: the reason you got an error is because not all code-paths had a return statement attached (in this case the "no content in the array" path).

[RockSolid1106]

35 minutes ago, minibois said:

I assumed you wanted the function to look at the entire array?

Yes, and the for-loop did that right? So the for loop basically loops through every item in the array and then checks if it matches the needle. If it does, return true, and that's my understanding. You imply that my code only checks the first word, but I beg to differ. 

 

The code works with the changes you and @Trinopoty suggested.

[RockSolid1106]

Oh I am extremely sorry, I got what you meant. The loop will immediately exit and return false when it does not see the first word in the array as the needle.

 

EDIT: Marking @minibois's answer as the solution, because it described exactly what the issue was.

Edited July 16, 2021 by RockSolid1106

[minibois]

4 minutes ago, RockSolid1106 said:

Oh I am extremely sorry, I got what you meant. The loop will immediately exit and return false when it does not see the first word in the array as the needle.

Exactly, you got it

The for-loop was the perfect approach to check over all the words in the array. The "return false" in the for-loop just meant it would only check the first word in the array and never the second, third, etc.

[Eigenvektor]

One minor note: You should be using "boolean", not "Boolean" unless you explicitly need to be able to also return null values.

 

"Boolean" is a reference type can can be null, true and false. If you do not initialize it, it defaults to null.

"boolean" is a primitive type and can only be true or false (and defaults to false).

 

Technically someone using your method needs to check for null, because your method could possibly return a null value.