i'm trying to write a code that masks red and blue channel from the image inputted.I have retrieved r,g,b values but however stuck up in proceeding further.I'm just a beginner.Can anyone help me in this please?

public class Green
    public static void main(String args[]) throws IOException

        BufferedImage bi= ImageIO.read(new File( "image.jpg" );      
        for (int x=0; x <= bi.getWidth(); x++){          
      for (int y = 0; y <= bi.getHeight(); y++){                         
         int pixelCol=bi.getRGB(x,y);              
       int r= (pixelCol>>16) & 0xff;
      int b = pixelCol & 0xff;
         int g = (pixelCol>>8) & 0xff;
              int px=0;

You have code to split out the RGB values from each pixel, so now you need some similar code to combine RGB values into a single int pixel. Between splitting them and re-combining them you can set r, g, and/or b to zero.

Or, you can use bi.getRaster().getDataBuffer(); to get direct (RW) access to the pixels, so you can modify and replace them one at a time. You can use & to zero out individual bytes each pixel.