Problem in passing color as a parameter

[Punit Jain]

Hello everyone, below code is for bounce multiple balls, my code is working correctly, but when i m trying to add Color also as a parameter, it not changing the color of the balls, code is:

Point.java

import java.applet.*;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
public class Point extends Applet implements Runnable{
	
	private Image i;
	private Graphics doubleG;
	Cfish f,f1,f2;
	public void init()
	{
		setSize(800,600);
		
	}
	public void start()
	{
		f = new Cfish();
		f1 = new Cfish(250,250);
		f2 = new Cfish(350,350);
		Thread thread = new Thread(this);//if this confuses run method can also be done here...
		thread.start();
	}
	public void run() {
		while(true)
		{
			f.update(this);
			f1.update(this);
			f2.update(this);
			repaint();
			try {
				Thread.sleep(17);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
	}
	
	
	public void update(Graphics g) {
		if(i == null)
		{
			i = createImage(this.getSize().width, this.getSize().height);
			doubleG = i.getGraphics();
		}
		doubleG.setColor(getBackground());
		doubleG.fillRect(0, 0,this.getSize().width, this.getSize().height);
		doubleG.setColor(getForeground());
		paint(doubleG);
		g.drawImage(i, 0, 0, this);
	
	}
	public void paint(Graphics g)
	{
		f.display(g);
		f1.display(g);
		f2.display(g);
	}
}

Cfish.java

import java.awt.Color;
import java.awt.Graphics;


public class Cfish {
	private int x = 400;
	private int y = 25;
	private int dx = 10;
	private int dy = 2;
	private int radius = 20;
	public Cfish() {
		// TODO Auto-generated constructor stub
	}
	public Cfish(int i, int j)
	{
		x = i;
		y = j;
	}
	public void update(Point sp)
	{
		if(x+dx>sp.getWidth()-radius-1)
		{
			x = sp.getWidth()-radius-1;
			dx = -dx;
		}
		else if(x+dx<0+radius)
		{
			x = 0+radius;
			dx = -dx;
		}
		else{
		x+= dx;
		}
		

		if(y+dy>sp.getHeight()-radius-1)
		{
			y = sp.getHeight()-radius-1;
			dy = -dy;
		}
		else if(y+dy<0+radius)
		{
			y = 0+radius;
			dy = -dy;
		}
		else{
		y+= dy;
		}
		y+= dy;
		
	}

	public void display(Graphics g)
	{
		g.setColor(Color.GREEN);
		g.fillOval(x-radius, y-radius, radius*2, radius*2);
	}
}

it's working fine but when i m adding color as a argument like this:

replace the point.java paint method:

public void paint(Graphics g, Color color)
	{
		f.display(g, Color.GREEN);
		f1.display(g, Color.BLUE);
		f2.display(g, Color.BLACK);
	}
	

replace the Cfish.java display method:

public void display(Graphics g, Color color)
	{
		g.setColor(color);
		g.fillOval(x-radius, y-radius, radius*2, radius*2);
	}

now it's not working..

how can i pass color as a parameter...??

[Rob Spoor]

When you add a parameter to the paint method, you are no longer overriding it but overloading it instead. You need to keep a reference (instance field) to the color to use.

[Punit Jain]

can you please explain..?

[Rob Spoor]

You know how to create an instance variable of type Color, don't you? Then you change display as you've tried before. paint keeps the same parameter list as originally though (only Graphics), and uses the instance variable in the calls to display.

[Punit Jain]

okay i got it, here is the code:

public void paint(Graphics g)
	{
		f.display(g, Color.CYAN);
		f1.display(g, Color.BLUE);
		f2.display(g, Color.RED);
		f3.display(g, Color.GRAY);
	}

public void display(Graphics g, Color color)
	{
		g.setColor(color);
		g.fillOval(x-radius, y-radius, radius*2, radius*2);
	}

[Rob Spoor]

[Punit Jain]

i want to know one more thing in this, how can i make this code into more object oriented form, is it possible?