java testing if double is an int

Question

Part of my program tests if two numbers are equal. Because certain operations take only doubles and others take only ints, I am comparing ints and doubles. The programs is returning that the two are equal even when they only round to being equal (i.e. 7.5=7). I only want the program to return true if the two actually are equal. I've tried the solutions listed here: How to test if a double is an integer to determine if my doubles are ints.
All of them appear to work - they compile, but the program still returns 7=7.5 I've tried going the other direction also - converting my ints to doubles - same result. How do I get my program to acknowledge the difference? With the most current suggestion:

import acm.program.ConsoleProgram;
import java.awt.Color;
import  acm.io.IODialog;
import java.text.*;
import static java.lang.Math.*;
import java.util.*;

/** Tests to see if user color matches sample colors */
public class ColorMatch extends ConsoleProgram
{
//defining sample colors
Color[] dmc =
{
    new Color(255,255,255),
    new Color(43,57,41),
    new Color(213,39,86),
    new Color(0,160,130),
    new Color(0,0,0),
};

public void run()
{
    average();

}

//averages three colors, then tests for match to given color
public void average()
{
    //asks for stitch color
    IODialog dialog     = new IODialog();
    int stitchRed       = dialog.readInt("Enter red value: ");
    int stitchGreen     = dialog.readInt("Enter green value: ");
    int stitchBlue      = dialog.readInt("Enter blue value: ");
    Color stitchColor   = new Color(stitchRed,stitchGreen,stitchBlue);

    //gets averages for dmc colors
    for (Color i:dmc)
    {
        for (Color j:dmc)
        {
            for (Color k:dmc)
            {
                int indexI = Arrays.asList(dmc).indexOf(i);
                int indexJ = Arrays.asList(dmc).indexOf(j);
                int indexK = Arrays.asList(dmc).indexOf(k);
                if  (indexI <= indexJ && indexJ <= indexK)
                {
                    int iRed = i.getRed();
                    int jRed = j.getRed();
                    int kRed = k.getRed();
                    int iGreen = i.getGreen();
                    int jGreen = j.getGreen();
                    int kGreen = k.getGreen();
                    int iBlue = i.getBlue();
                    int jBlue = j.getBlue();
                    int kBlue = k.getBlue();
                    double redAverage   = (iRed+jRed+kRed)/3;
                    double greenAverage = (iGreen+jGreen+kGreen)/3;
                    double blueAverage  = (iBlue+jBlue+kBlue)/3;
                    if (redAverage == (int)redAverage && greenAverage == (int)greenAverage && blueAverage == (int)blueAverage)
                    {
                        int rAverage = (int)redAverage;
                        int gAverage = (int)greenAverage;
                        int bAverage = (int)blueAverage;
                        Color colorAverage = new Color(rAverage,gAverage,bAverage);

                        //tests to see if any average equals the stitch color
                        if (colorAverage.equals(stitchColor))
                        {
                            println("The color match is: " + i + ", " + j + ", " + k);
                        }
                    }
                }
            }
        }
    }

I plugged in 85s as my test numbers.
The only result should be (0,0,0)+(0,0,0)+(255,255,255), but it is also yielding (43,57,41)+(213,39,86)+(0,160,130) . (41+86+130)/3=85.7!=85.

Also, try looking at this question for your issue with doubles and ints: http://stackoverflow.com/q/9898512/5335355 — CShark, Aug 20 '16 at 16:17

score 0 · Answer 1 · edited May 23 '17 at 12:23

0

I think the problem is that you are making a comparison of the 'int' and the 'double' values after casting the double value to int which truncates the decimal part. For example (7==7.5) is false, but (7==(int)7.5) is true because (int)7.5 = 7. So if you want strict comparison between an int and a double, you can compare them straight forward without casting. If you want to know more on how casting double to int works, please refer How does double to int cast work in Java.

edited May 23 '17 at 12:23

Community

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answered Aug 20 '16 at 13:23

Addis

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I'm comparing the double value: redAverage to the truncated integer of redAverage If they are equal, then redAverage should be an int. I have alternatively compared it using the floor function for redAverage. I've also comared the floor and ceiling of redAverage. I used the solutions listed here: http://stackoverflow.com/questions/9898512/how-to-test-if-a-double-is-an-integer – Molly Kitti Aug 21 '16 at 01:29

java testing if double is an int

1 Answers1