Is there a library to compare primitive type values?

Question

I am implementing Comparable interface on a trivial class that wraps a single int member.

I can implement it this way:

    @Override
    public int compareTo ( final MyType o )
    {
        return
            Integer.valueOf( this.intVal ).compareTo(
                Integer.valueOf( o.intVal )
            );
    }

But this (maybe) creates 2 totally unnecessary Integer objects.

Or I can go tried and true cut-and-paste approach from Integer class:

    @Override
    public int compareTo ( final MyType o )
    {
      int thisVal = this.intValue;
      int anotherVal = o.intValue;
      return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1));
    }

This is pretty efficient, but duplicates code unnecessary.

Is there a library that would implement this missing Integer ( and Double and Float ) method?

   public static int compare ( int v1, int v2 );

Could you copy the Integer `compareTo()` to a new method that takes two arguments instead of using `this`? — BenCole, Sep 01 '11 at 16:10

score 6 · Accepted Answer · answered Jul 31 '13 at 11:07

In Java 7, static int compare for primitive types have been added to all primitive object wrapper classes, i.e there is now:

java.lang.Integer: static int compare( int x, int y );
java.lang.Byte: static int compare( byte x, byte y );
java.lang.Short: static int compare( short x, short y );
etc...

NPE · Answer 2 · 2011-09-01T16:25:25.777

6

For int, write your own compare method (it requires at most three lines of code).
For double, use Double.compare (not to be confused with compareTo).
For float, use Float.compare.

The last two take primitive types and thus avoid boxing and unboxing. I can see an argument for Integer providing a similar compare method, but as things stand it doesn't.

edited Sep 01 '11 at 16:25

answered Sep 01 '11 at 16:14

NPE

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`Integer` also has a `compare` – Steve Kuo Sep 01 '11 at 16:18
@Steve Kuo: Link to Javadoc please? – NPE Sep 01 '11 at 16:18
You are correct. I was thinking of `compareTo`, in which case he could do `Integer.valueOf(i1).compareTo(i2)`. – Steve Kuo Sep 01 '11 at 16:24
@Steve Kuo: No, it doesn't, that's the point. And, by the way, if you've read the question I know how to do `Integer.valueOf` – Alexander Pogrebnyak Sep 01 '11 at 16:26
+1: For byte, short, int and float you can use Double.compare(). – Peter Lawrey Sep 01 '11 at 19:14

score 2 · Answer 3 · answered Sep 01 '11 at 16:10

2

Maybe, I'm missing something, but IMHO this is a weird question.

Is there a library that would implement this missing Integer ( and Double and Float ) method?
public static int compare ( int v1, int v2 );

Well, I think this does the job:

public static int compare ( int v1, int v2 )
{
    if (v1 < v2) return -1;
    if (v1 > v2) return  1;
    return 0;
}

answered Sep 01 '11 at 16:10

Martijn Courteaux

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@barjak: Nope, please check http://stackoverflow.com/questions/7273091/is-there-a-library-to-compare-primitive-type-values/7273222#7273222 and it comments. – Martijn Courteaux Sep 01 '11 at 16:20

Bohemian · Answer 4 · 2011-09-01T16:22:37.770

-1

This solution is simple, but perhaps simplistic:

public static int compare ( int v1, int v2 )
{
    return v1 - v2;
}

Note: @aix is correct! This approach will not work for arbitrary integers. It will work for always-positive integers though, for example auto generated database keys etc

edited Sep 01 '11 at 16:22

answered Sep 01 '11 at 16:16

Bohemian

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How about integer overflow? – NPE Sep 01 '11 at 16:17
1

@Martijn Courteaux, you are incorrect, `compare` and `compareTo` specify negative, 0, positive values. It doesn't dictate -1, 0 1. Any code that checks for -1 is bad and broken code. See http://download.oracle.com/javase/6/docs/api/java/lang/Comparable.html#compareTo%28T%29 – Steve Kuo Sep 01 '11 at 16:20
1

No, the Javadoc says "negative, zero or positive", for both Comparable and Integer. – barjak Sep 01 '11 at 16:22
@Steve Kuo: Oops, indeed! Thanks, I learnt something today :D – Martijn Courteaux Sep 01 '11 at 16:23

Is there a library to compare primitive type values?

4 Answers4