CODEWITHSUNDEEP
javaperformancedoubleboxing
user710818
user710818

Reputation: 24248

Is performance of "Math.abs()" better than expression with "if"?

I have expression:

Double getAbs(Double value){
return value> 0 ? value: value== 0 ? null : -value;
}

or better:

 Double getAbs(Double value){
return Math.abs(value);
}

I understand that there are some differences about NaN. But method Math.abs(double) - so we have unboxing. In which case performance better?

Upvotes: 3

Views: 9389

Answers (3)

Jagat
Jagat

Reputation: 1392

I just had a look at SunOracle's implementation and this is how they've implemented it

public static double abs(double a) {
    return (a <= 0.0D) ? 0.0D - a : a;
}

Except for the cost of unboxing and autoboxing params and return values, there shouldn't be any other performance impact.

Upvotes: 4

Buhake Sindi
Buhake Sindi

Reputation: 89169

The only "performance" in your code is that the JVM will need to unbox your Double to double.

Math.abs(double) uses a ternary if statement as follows:

public static double abs(double a) {
    return (a <= 0.0D) ? 0.0D - a : a;
}

So, your if statement is no performance worry at all.

Upvotes: 8

masoud
masoud

Reputation: 56479

No usually, Math.abs() is not slower than yours. Because JVM can implement its math operation according to the target machine. and It can be faster than your implementation.

Code generators are encouraged to use platform-specific native libraries or microprocessor instructions, where available, to provide higher-performance implementations of Math methods. Such higher-performance implementations still must conform to the specification for Math.

For more information read this.

Anyway, if you need better performance -in this case- you can use double instead of Double and forget your getAbs() and use Math.abs() directly.

Upvotes: 4

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