Convert a RGB Color Value to a Hexadecimal String

In my Java application, I was able to get the Color of a JButton in terms of red, green and blue; I have stored these values in three ints.

How do I convert those RGB values into a String containing the equivalent hexadecimal representation? Such as #0033fA

You can use

String hex = String.format("#%02x%02x%02x", r, g, b);  

Use capital X's if you want your resulting hex-digits to be capitalized (#FFFFFF vs. #ffffff).

A one liner but without String.format for all RGB colors:

Color your_color = new Color(128,128,128);

String hex = "#"+Integer.toHexString(your_color.getRGB()).substring(2);

You can add a .toUpperCase()if you want to switch to capital letters. Note, that this is valid (as asked in the question) for all RGB colors.

When you have ARGB colors you can use:

Color your_color = new Color(128,128,128,128);

String buf = Integer.toHexString(your_color.getRGB());
String hex = "#"+buf.substring(buf.length()-6);

A one liner is theoretically also possible but would require to call toHexString twice. I benchmarked the ARGB solution and compared it with String.format() and the toHexString solution has a much higher performance:

Random ra = new Random();
int r, g, b;
r=ra.nextInt(255);
g=ra.nextInt(255);
b=ra.nextInt(255);
Color color = new Color(r,g,b);
String hex = Integer.toHexString(color.getRGB() & 0xffffff);
if (hex.length() < 6) {
    hex = "0" + hex;
}
hex = "#" + hex;

Convert a java.awt.Color to a 24-bit hexadecimal RGB representation even if alpha channel value is zero (e.g. 0000ff):

String.format("%06x", 0xFFFFFF & Color.BLUE.getRGB())

For uppercase (e.g. 0000FF) :

String.format("%06X", 0xFFFFFF & Color.BLUE.getRGB())

This is an adapted version of the answer given by Vivien Barousse with the update from Vulcan applied. In this example I use sliders to dynamically retreive the RGB values from three sliders and display that color in a rectangle. Then in method toHex() I use the values to create a color and display the respective Hex color code. >This example does not include the proper constraints for the GridBagLayout. Though the code will work, the display will look strange.

public class HexColor
{

  public static void main (String[] args)
  {
   JSlider sRed = new JSlider(0,255,1);
   JSlider sGreen = new JSlider(0,255,1);
   JSlider sBlue = new JSlider(0,255,1);
   JLabel hexCode = new JLabel();
   JPanel myPanel = new JPanel();
   GridBagLayout layout = new GridBagLayout();
   JFrame frame = new JFrame();

   //set frame to organize components using GridBagLayout 
   frame.setLayout(layout);

   //create gray filled rectangle 
   myPanel.paintComponent();
   myPanel.setBackground(Color.GRAY);

   //In practice this code is replicated and applied to sGreen and sBlue. 
   //For the sake of brevity I only show sRed in this post.
   sRed.addChangeListener(
         new ChangeListener()
         {
             @Override
             public void stateChanged(ChangeEvent e){
                 myPanel.setBackground(changeColor());
                 myPanel.repaint();
                 hexCode.setText(toHex());
         }
         }
     );
   //add each component to JFrame
   frame.add(myPanel);
   frame.add(sRed);
   frame.add(sGreen);
   frame.add(sBlue);
   frame.add(hexCode);
} //end of main

  //creates JPanel filled rectangle
  protected void paintComponent(Graphics g)
  {
      super.paintComponent(g);
      g.drawRect(360, 300, 10, 10);
      g.fillRect(360, 300, 10, 10);
  }

  //changes the display color in JPanel
  private Color changeColor()
  {
    int r = sRed.getValue();
    int b = sBlue.getValue();
    int g = sGreen.getValue();
    Color c;
    return  c = new Color(r,g,b);
  }

  //Displays hex representation of displayed color
  private String toHex()
  {
      Integer r = sRed.getValue();
      Integer g = sGreen.getValue();
      Integer b = sBlue.getValue();
      Color hC;
      hC = new Color(r,g,b);
      String hex = Integer.toHexString(hC.getRGB() & 0xffffff);
      while(hex.length() < 6){
          hex = "0" + hex;
      }
      hex = "Hex Code: #" + hex;
      return hex;
  }
}

A huge thank you to both Vivien and Vulcan. This solution works perfectly and was super simple to implement.

slightly modified versions for RGBA from https://stackoverflow.com/questions/6539879/how-to-convert-a-color-integer-to-a-hex-string-in-android/ and https://stackoverflow.com/questions/18914341/how-to-code-and-decode-rgb-to-hex

    public static String ColorToHex (Color color) {
    int red = color.getRed();
    int green = color.getGreen();
    int blue = color.getBlue();
    int alpha = color.getAlpha(); 

    String redHex = To00Hex(red);
    String greenHex = To00Hex(green);
    String blueHex = To00Hex(blue);
    String alphaHex = To00Hex(alpha);

    // hexBinary value: RRGGBBAA
    StringBuilder str = new StringBuilder("#");
    str.append(redHex);
    str.append(greenHex);
    str.append(blueHex);
    str.append(alphaHex);

    return str.toString();
}

private static String To00Hex(int value) {
    String hex = "00".concat(Integer.toHexString(value));
    hex=hex.toUpperCase();
    return hex.substring(hex.length()-2, hex.length());
} 

another way, this one could be related to the benchmark above:

public static String rgbToHex (Color color) {

   String hex = String.format("#%02x%02x%02x%02x", color.getRed(), color.getGreen(), color.getBlue(), color.getAlpha() );
   hex=hex.toUpperCase();
       return hex;
}

a very simple benchmark shows that solution with String.format is 2+ times slower than StringBuilder for 10 million color conversions. For small amount of objects you cannot really see a difference.

I am not an expert so my opinion is subjective. I'm posting the benchmark code for any use, replace methods rgbToHex, rgbToHex2 with those you want to test:

   public static void benchmark /*ColorToHex*/ () {
       
 Color color = new Color(12,12,12,12);
   
     ArrayList<Color> colorlist = new ArrayList<Color>();
    // a list filled with a color i times
    for (int i = 0; i < 10000000; i++) {
      
        colorlist.add((color));
    }
   
   ArrayList<String> hexlist = new ArrayList<String>();
   System.out.println("START TIME... " + ZonedDateTime.now().format(DateTimeFormatter.ISO_LOCAL_TIME) + "  TEST CASE 1...");
        for (int i = 0; i < colorlist.size(); i++) {
        hexlist.add(rgbToHex(colorlist.get(i)));
    }
        System.out.println("END TIME... " + ZonedDateTime.now().format(DateTimeFormatter.ISO_LOCAL_TIME) + "  TEST CASE 1...");
        System.out.println("hexlist.get(0)... "+hexlist.get(0));
        
     ArrayList<String> hexlist2 = new ArrayList<String>();
   System.out.println("START TIME... " + ZonedDateTime.now().format(DateTimeFormatter.ISO_LOCAL_TIME) + " TEST CASE 2...");
        for (int i = 0; i < colorlist.size(); i++) {
        hexlist2.add(rgbToHex1(colorlist.get(i)));
    }
     System.out.println("END TIME... " + ZonedDateTime.now().format(DateTimeFormatter.ISO_LOCAL_TIME) + "  TEST CASE 2..."); 
     System.out.println("hexlist2.get(0)... "+hexlist2.get(0));

    }

it seems that there are issues with Integer.toHexString(color.getRGB()) try it with Color color = new Color(0,0,0,0); and you will find out that we have subtraction of zeros. #0 instead of #00000000 and we need all digits in order to have valid hex color values, 6 or 8 if with Alpha. So as far as I can see we need an improved use of Integer.toHexString to handle those cases. There should be other cases that cannot handle leading zeros at hex values. For example try with #0c0c0c0c that corresponds to Color color = new Color(12,12,12,12); The result will be #C0C0C0C witch is wrong.