Comparable and compareTo() error: Cannot invoke compareTo(float) on the primitive type float

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almost_sc..

Comparable and compareTo() error: Cannot invoke compareTo(float) on the primitive type float

in Programming Questions • 1 year ago

Hi!

I'm trying to implement a Comparable for the first time and having some (I suspect) is a casting issue.

I've got a simple myRect class that creates a Rect and Polygon2d (via Toxilibs). I've got a List of these myRects that I'm trying to sort first by height and then by width.

Here is the code:

import toxi.geom.*;
import toxi.geom.mesh2d.*;
import toxi.processing.*;
import toxi.geom.mesh.*;
import toxi.math.conversion.*;
import java.util.Comparator;
List<myRect> rects = new ArrayList<myRect>();
int nRects=5;
ToxiclibsSupport gfx;
void setup() {
gfx=new ToxiclibsSupport(this);
size(500, 500);
// translate(250,250);
for (int i=0; i<nRects; i++) {
println(i);
rects.add( new myRect(100,500) );
noFill();
gfx.polygon2D(rects.get(i).polyR);
}
}
public class myRect implements Comparable<myRect> {
Rect r;
Polygon2D polyR;
float w, h, a;
public myRect(float f1, float f2) {
r = new Rect( new Vec2D(random(f1, f2), random(f1, f2)), new Vec2D(random(f1, f2), random(f1, f2)) );
polyR=r.toPolygon2D();
if (polyR.isClockwise()) {
polyR.reverseOrientation();
}
// w=r.width;
// h=r.height;
//
}
public int compareTo(myRect inr) {
int lastCmp = this.r.height.compareTo(inr.r.height);
return (lastCmp != 0 ? lastCmp :
r.width.compareTo(inr.r.width));
}
}

On the line " int lastCmp = this.r.height.compareTo(inr.r.height);", line 46 above, I get the error:

Cannot invoke compareTo(Float) on the primitive type float

I've cribbed this code from the Java Tutorial, and according to the Toxilibs Java doc for the Rect class, the height field is a float.

I've tried a few things but can't seem to get pas this error.

Like I said this is my first time implementing and using Comparable and compareTo so I'm probably making a simple mistake. And I know there is a simpler way to directly compare the width and height, however, I really want to learn how to use comapreTo properly.

Can anyone point out what I'm doing wrong?

Thanks in advance!

Replies(3)

almost_sc..

Re: Comparable and compareTo() error: Cannot invoke compareTo(float) on the primitive type float

1 year ago

And, of course, soon after posting to the forum I figure it out.

Changing the compareTo function to explicitly cast the width and height as Float objects, not float primitives, like so:

public int compareTo(myRect inr) {
Float thisHeight=new Float( this.r.height );
Float thatHeight=new Float( inr.r.height );
Float thisWidth=new Float( this.r.width );
Float thatWidth=new Float( inr.r.width );
int lastCmp = thisHeight.compareTo(thatHeight);
return (lastCmp != 0 ? lastCmp :
thisWidth.compareTo(thatWidth));
}

This illuminated the error (and makes sense to me). So on to the next problem ;)

Hop this helps someone else!

PhiLho

Re: Comparable and compareTo() error: Cannot invoke compareTo(float) on the primitive type float

1 year ago

Well, unless you think you can have NaN or negative zeroes in your dimensions, it is simpler to do:

public int compareTo(myRect inr) {
if (height < r.height) return -1;
if (height > r.height) return 1;
if (width < r.width) return -1;
if (width > r.width) return 1;
return 0; // They are equal
}

and more efficient, as you don't create lot of objects...

almost_sc..

Re: Comparable and compareTo() error: Cannot invoke compareTo(float) on the primitive type float

1 year ago

Yeah, I caught those negative dimensions right after I got the code running and redefined how I make them, really they are just placeholders for now. But thanks for the suggestion on how to use compareTo without creating Float objects.

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