随机圈小程序Java

Question

I am new to programming and trying to write a graphics program in java that displays ovals of different sizes and colors, however, I am not able to get the program to display the ovals in applet window. Does anyone have any suggestions/input on where I went wrong here? Please see an example of my paint method below:

   public void paint(Graphics g)
   {
    for(int i=0; i<n; i++)
   {
     x[i] = (int)(600* Math.random() +1);
         y[i] = (int)(600* Math.random() +1);
   }
    int c= (int)(255*Math.random()); //random foreground color
    int a= (int)(255*Math.random());
    int t= (int)(255*Math.random());

    Color f = new Color(c,a,t);//variables have been declared in init
    g.setColor(f);
    g.fillOval(rand(0, 600), rand(0, 600), r = rand(5, 100), r);
    sleep(100);
    cnt += 1;
    if(cnt >= 500) clearScreen();
    else  update(g);
  }

Answer 1

I modified a recent school project (we were supposed to make a hot air balloon) so excuse the naming of some of the stuff:

import java.awt.*;
import javax.swing.*;

public class Balloon extends JComponent {
    public static void main(String args[]){
        JFrame frame = new JFrame("balloons");
        frame.setSize(200,200);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        Balloon balloon = new Balloon();
        frame.setContentPane(balloon);
    }
    public void paint(Graphics g){
        super.paint(g);

        for(int i = 0; i<20; i++){
            int c= (int)(255*random()); //random foreground color
            int a= (int)(255*random());
            int t= (int)(255*random());
            g.setColor(new Color(c,a,t));
            g.fillOval((int)(200*random()),(int)(200*random()),(int)(30*random()),(int)(30*random()));
        }
    }
    public double random(){
        return Math.random();
    }
}

Its rather small at the moment so you may want to change around some of the variables... however it does what you asked.

In terms of where you went wrong... it appears you have a loop that put values into two arrays... however I don't see a second array that goes through and draws all the ovals... In my code, I generate all the coordinates, colours, and print it out all at once.