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Returning a Java Boolean Method

I have a boolean method in my Java program and am wondering why NetBeans recommends making this change to my code:

return isPrime != 0;

I wrote:

if (isPrime == 0) {
            return false;

        }
        else{
            return true;
        }

Both work correctly, but I cannot understand the logic behind the changes that NetBeans offers. Neither true nor false is returned. Can anyone explain to me the logic behind this? Thanks to

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6 answers


Instead

if (isPrime == 0) {
    return false;
} else {
    return true;
}

try

return (isPrime != 0);

It's the same, I'll show you the refactoring path. Beginning with

if (isPrime == 0) {
    return false;
} else {
    return true;
}

coincides with

if (isPrime != 0) {
    return true;
} else {
    return false;
}

which can be reduced by substitution, substituting 'isPrime! = 0' with the function 'doIsPrime ()'

private boolean doIsPrime() {
   return isPrime != 0;
}


substituting in

if (doIsPrime()) {
    // guaranteed to be the same as above!
    return doIsPrime();
} else {
    return doIsPrime();
}

which can have both minified blocks (like duplicate code)

if (doIsPrime()) {
}
return doIsPrime();

And reduced further by removing the if statement around the empty block

return doIsPrime();

Now undo replacing 'doIsPrime ()' back with 'isPrime! = 0'

return isPrime != 0;

There was no need to make a replacement; but, I find it better shows that the if argument is redundant.

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NetBeans is exactly right. The expression is logical. You can easily prove this by making changes and trying them out.

What does it matter 0 != 0

? (Hint: this false

). What about 1 != 0

? (Hint: this true

).



Is that not what your more verbose code says?

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Doesn't return true or false.

False. Comparison result isPrime != 0

, a is boolean

returned, either true

or false

.

Can anyone explain to me the logic behind this?

The first code is equivalent to the second code. If isPrime

- 0

, return false

, else return true

. The operator !=

will give false

if isPrime

- 0

and true

if not 0

.

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This means it returns the result of the predicate isPrime != 0

If isPrime = 0 then the predicate is false, so it returns false If isPrime! = 0 then the predicate is true, so it returns true

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This is just to keep the code short.

The expression isPrime != 0

returns a boolean value. This is not true if isPrime == 0

and true if isPrime != 0

. This way you can keep the if statement and some lines of code.

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Just to add to that said:

While your solution and the NetBeans recommended approach are accurate, another approach would also be:

if (isPrime == 0) {
    return false;
}

return true;

I don't know what NetBeans will suggest with this approach, but I guess it will offer the same recommendation as above.

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