Is it valid to compare a double with an int in java?

Question

Utilities.getDistance(uni, enemyuni) <= uni.getAttackRange()

Utilities.getDistance returns double and getAttackRange returns int. The above code is part of an if statement and it needs to be true. So is the comparison valid?

Thanks

Solution 1

Yes, it's valid - it will promote the int to a double before performing the comparison.

See JLS section 15.20.1 (Numerical Comparison Operators) which links to JLS section 5.6.2 (Binary Numeric Promotion).

From the latter:

Widening primitive conversion (§5.1.2) is applied to convert either or both operands as specified by the following rules:

• If either operand is of type double, the other is converted to double.

• ...

Solution 2

When performing operations (including comparisons) with two different numerical types, Java will perform an implicit widening conversion. This means that when you compare a double with an int, the int is converted to a double so that Java can then compare the values as two doubles. So the short answer is yes, comparing an int and a double is valid, with a caveat.

The problem is that that you should not compare two floating-piont values for equality using ==, <=, or >= operators because of possible errors in precision. Also, you need to be careful about the special values which a double can take: NaN, POSITIVE_INFINITY, and NEGATIVE_INFINITY. I strongly suggest you do some research and learn about these problems when comparing doubles.

Solution 3

This should be fine. In floating point operation/comparisons, if one argument is floating/double then other one being int is also promoted to the same.

Solution 4

yes it is absolutely valid compare int datatype and double datatype..

int i =10;
double j= 10.0;
 if (i==j)
{
System.out.println("IT IS TRUE");
}

Solution 5

Yes it valid, and your code should work as expected without any glitch, but this is not the best practice, static code analyzers like SonarQube shows this as a "Major" "Bug",

Major Bug img from sonarQube

Major Bug description from sonarQube

so, the right way to do this can be,

Double.compare(val1,val2)==0 

if any parameter are not floating point variable, they will be promoted to floating point.

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Comments

[Tasos]

Funny thing is this is my professors code. But yea I will investigate the subject now

[Code-Apprentice]

You must be careful (and usually even avoid) comparing floating-point values with the == operator.

[Code-Apprentice]

@Crone For a school assignment, you probably can ignore these edge cases, but you should still know about them. Choosing to ignore them is preferrably than complete ignorance.

[Mickäel A.]

And what do you want to compare these 2 values with ?

[Marko Topolnik]

All ints are exactly representable as double.

[Marko Topolnik]

I don't see anything wrong with comparing a double with <= or >= against an int. Only exact equality might be questionable.

[Code-Apprentice]

@MarkoTopolnik <= or >= may give undesirable results in some cases, just like == does.

[Marko Topolnik]

"Some cases" is not as unpredictable as you picture it and when calculating Euclidian distance, it would be perfectly alright.

[Code-Apprentice]

@MarkoTopolnik Granted, it is not entirely unpredictable, just as it is not with ==. There is plenty of information available about comparing floating point values for equality, so if the OP needs/wants more detail, they can research it further.

[Tasos]

Yea I can understand this is a case of way too much detail for a university code. I also completely agree with the fact that tmi can be really harmful when you start to learn a language. Thanks a lot for the input guys

[Daniel]

All Integers up to 2^52 are exactly represented as double. So there is no problem to compare int with double, even for equality, if you know it stores an integer, which could be not true if you operate over that variable.