Checking the “boolean” result of an “int” type

Question

I\'m learning Java, coming from C and I found an interesting difference between languages with the boolean type. In C there is no bool/ean

Answer 1

In Java,

if ( i != 0 )

is the idiomatic way to check whether the integer i differs from zero.

If i is used as a flag, it should be of type boolean and not of type int.

Answer 2

Probably something like this:

int i == 0 ? false : true;

or the other way round:

int i == 1 ? true : false

...

Answer 3

If you insist to use int instead of boolean, just use a method to convert

class BooleanHelper
{
   public static boolean toBoolean (int pVal) {
      return pVal != 0;
   }
 ...
}

// apply

if (BooleanHelper.toBoolean(i)) { // BooleanHelper could be avoided using static imports...

However, just use

if (i != 0) {

is still shorter and clearer.

Answer 4

Why not use the boolean type ? That will work as you expect without the potentially problematic integer/boolean conflation.

private boolean isValid;
...
if (!isValid) {
   ...
}

Note that this is the idiomatic Java approach. 3rd party libs use this, and consumers of your API will use and expect it too. I would expect libs that you use to give you booleans, and as such it's just you treating ints as booleans.

Answer 5

FROM JLS:

The boolean type has two values, represented by the boolean literals true and false, formed from ASCII letters.

Thus no is the answer. the only was is

if ( i != 0 )

Answer 6

In java the condition has to be of type boolean else it can't be an expression, that is why

if( i ) 

is not allowed.

It has to be either true or false.