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Using Java Random Class

Please help. I am trying to use the Java Random class to draw spirals of random locations, size, color, etc. on drawing canvas. I am able to get the Random class to work when I call my drawCurvedSpiral method. However, sometimes it will print some of my spirals partially off the screen. So, how can I prevent this from happening?
Below is what I have...
import java.awt.Graphics;
import java.awt.Color;
import java.util.Random;
public class AbstractArt
{
public static void main(String[] args)
{
DrawingCanvas canvas = new DrawingCanvas();
Graphics g = canvas.getGraphics();
Random rand = new Random();
for (int i = 0; i < 10; i++)
{
int width = 25 + rand.nextInt(76);
int arc = 0 + rand.nextInt(361);
int x = rand.nextInt(canvas.getWidth()-width);
int y = rand.nextInt(canvas.getHeight()-width);
drawCurvedSpiral(g, x, y, width, width, arc, arc, getRandomCOlor());
}
}

How to randomly repaint lines between three different colors

I have every part of this program working except for the colors. Right now I have it repainting any random color and I need it to only paint the lines yellow, green, or blue. Can someone lead me in the right direction please?
`package ColoredLines;
import java.awt.Graphics;
import java.util.Random;
import javax.swing.JPanel;
import java.awt.Color;
#SuppressWarnings("serial")
public class ColoredLines extends JPanel {
private final Random rand = new Random();
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Random rand = new Random();
super.paintComponent(g);
this.setBackground(Color.BLACK);
for(int i = 10; i < 410; i += 20){
for(int j = 0; j < 410; j += 410){
g.setColor(new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256)));
g.fillRect(i, j, 10, 410);
}
}
}
}
`

Make an ArrayList of the three colors:
ArrayList<Color> colors = new ArrayList<Color>();
Add three colors with: colors.add(new Color(r,g,b)
To select a random color using:
Random rand = new Random();
Color randomColor = colors[rand.nextInt(2)];
Note: in rand.nextInt(2); the random number could be 0, so the possible numbers are three (0,1,2).

Draw series of concentric circles with random settings

I'm really stuck on how to go about programming this. Need to draw a series of 8 concentric circles using Java drawArc method with following conditions
using import java.util.Random library
Provide for starting the drawings at random location (i.e., the x-y
cooridinate must be calculated randomly).
Provide a random color for each circle
Provide a random diameter for each circle
My current code is able to get random random color for each circle but not clear how to meet other random conditions
// Exercise 12.6 Solution: CirclesJPanel.java
// This program draws concentric circles
import java.awt.Graphics;
import javax.swing.JPanel;
public class ConcentricCircles extends JPanel
{
// draw eight Circles separated by 10 pixels
public void paintComponent( Graphics g )
{
Random random = new Random();
super.paintComponent( g );
// create 8 concentric circles
for ( int topLeft = 0; topLeft < 80; topLeft += 10 )
{
int radius = 160 - ( topLeft * 2 );
int r = random.nextInt(255);
int gr = random.nextInt(255);
int b = random.nextInt(255);
Color c = new Color(r,gr,b);
g.setColor(c);
g.drawArc( topLeft + 10, topLeft + 25, radius, radius, 0, 360 );
} // end for
}
}
// This program draws concentric circles
import javax.swing.JFrame;
public class ConcentricCirclesTest extends JFrame {
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
JFrame frame=new JFrame("Concentric Circles");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ConcentricCircles cCirclesJPanel = new ConcentricCircles();
frame.add(cCirclesJPanel);
frame.setSize(200,250);
frame.setVisible(true);
}//end main
}

Several points are key to such an exercise:
Start with constants for the number of circles and step size; the random number generator in particular only needs to be created once.
private static final int N = 8;
private static final int S = 32;
private static Random random = new Random();
Choose a random point whose coordinates fall within the drawing area.
// a random point inset by S
int x = random.nextInt(getWidth() - S * 2) + S;
int y = random.nextInt(getHeight() - S * 2) + S;
For each circle, find the diameter as a function of S, adding a random fraction of a step, and render the arc at the chosen point offset by the radius.
for (int i = 0; i < N; i++) {
g2d.setColor(…);
int d = (i + 1) * S + random.nextInt(S / 2);
int r = d / 2;
g2d.drawArc(x - r, y - r, d, d, 0, 360);
}
Resize the enclosing frame, which forces a repaint(), to see the effect.
As random colors are not always appealing, consider Collections.shuffle() on a List<Color>.
private final List<Color> clut = new ArrayList<Color>();
…
for (int i = 0; i < N; i++) {
clut.add(Color.getHSBColor((float) i / N, 1, 1));
}
…
Collections.shuffle(clut);
…
g2d.setColor(clut.get(i));
Override getPreferredSize() to establsh the drawing panel's size.
private static final int W = S * 12;
private static final int H = W;
…
#Override
public Dimension getPreferredSize() {
return new Dimension(W, H);
See also Initial Threads.

Java Applet adding thread makes while loop infinite

I am trying to make a program that generates 25 random ovals then draw a ball and make it bounce, I got it somewhat done, I generated the ovals and I got the ball to move but when I added the thread it kept repeating the draw oval loop, I get somewhat why this is happening but I have no idea how to fix it.
Basically my program should:
draw 25 random sized ovals on random locations within the border - completed
draw a ball and make it move - completed
make the ball bounce - not done but I know how to do it
but it keeps repeating step one.
this is my code that I have written, oh and I have to use applets right now its part of the course please don't suggest I use swing or something else:
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
public class As4B extends Applet implements Runnable
{
public int x, y;
public int width = 854;
public int height = 480;
public int border = 20;
public Image offscreen;
public Graphics d;
public void init()
{
setSize(width,height);
Thread th = new Thread(this);
th.start();
offscreen = createImage(width,height);
d = offscreen.getGraphics();
}
public void run()
{
x = 100;
y = 100;
while(true)
{
x ++;
y ++;
repaint();
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public void paint(Graphics gfx)
{
d.setColor(java.awt.Color.black);
d.fillRect(0, 0, width, height);
d.setColor(java.awt.Color.green);
d.fillRect(0 + border, 0 + border, (width - (border * 2)), (height - (border* 2)));
genOval(25, d);
d.setColor(Color.gray);
d.fillOval(x, y, 50, 50);
gfx.drawImage(offscreen, 0, 0, this);
}
public int random(int low, int high)
{
int answer =(int)((Math.random()*(high-low))+ low);
return answer;
}
public void genOval(int amount, Graphics f)
{
int ranWidth, ranHeight, ranX, ranY, red, blue, green;
int i = 0;
while(i < 25)
{
green = random(0,255);
blue = random(0,255);
red = random(0,255);
f.setColor(new Color(red,green,blue));
ranWidth = random(30,400);
ranHeight = random(30,200);
ranX = random(0 + border, ((width - border)- (ranWidth)));
ranY = random(0 + border , ((height - border)- (ranHeight)));
f.fillOval(ranX, ranY, ranWidth, ranHeight);
i++;
}
}
public void update(Graphics gfx) {
paint(gfx);
}
}

Your genOval() method has no persistent backing. Every time repaint() is called (by your thread), the paint() method is called, and this generates new locations for the random ovals. You need to create a persistent source for that information, like so:
List<Rectangle> rectangles = new ArrayList<Rectangle>();
List<Color> colors = new ArrayList<Color>();
public void init() {
...
for (int i = 0; i < 25; i++) {
int green = random(0,255);
int blue = random(0,255);
int red = random(0,255);
colors.add(new Color(red,green,blue));
ranWidth = random(30,400);
ranHeight = random(30,200);
ranX = random(0 + border, ((width - border)- (ranWidth)));
ranY = random(0 + border , ((height - border)- (ranHeight)));
rectangles.add(new Rectangle(ranX, ranY, ranWidth, ranHeight));
}
}
public void genOval(Graphics g) {
for (int i = 0; i < 25; i++) {
Color color = colors.get(i);
Rectangle rectangle = rectangle.get(i);
// Draw using color & rectangle
}
}

Diffusing a color in java Draw

I am trying to diffuse a color in java Draw (which doesn't have the capability to diffuse normally) but I ran into an error and I can't seem to spot it.
The way I went about diffusing was by writing a small script that would draw my shape hundreds of times, each time smaller and slightly varying in color. This is my snippet:
import javax.swing.*;
import java.awt.*;
public class DiffuseDraw extends JFrame
{
//set size of window here
final int length = 350;
final int height = 370;
public DiffuseDraw()
{
super("Graphics Project Window");
Container container = getContentPane();
setBackground(new Color(0,0,0));
setSize(length, height);
setVisible(true);
}
// my problem comes here:
public void paint(Graphics g)
{
Draw.fillRectangle(g,0,0,length,height,new Color(19,24,32));
int rad = 325; // size of the biggest circle
float floatGreen = 0; // Color components for black
float floatBlue = 0;
float floatRed = 0;
int counter = 0; // the counter
while (counter < 290) {
rad = rad - 1; // Here we shrink the by a small incriment
floatRed = floatRed + 87/290; //red component slowly goes brighter
floatBlue = floatBlue + 178/290; // blue component slowly goes brighter
floatGreen = floatGreen + 211/290; // green component slowly goes brighter
int intRed = (int)Math.round(floatRed);
int intBlue = (int)Math.round(floatBlue);
int intGreen = (int)Math.round(floatGreen);
Draw.fillCircle(g,173,307,rad,new Color(intRed,intBlue,intGreen));
counter = counter + 1;
}
}
public static void main(String args[]) {
DiffuseDraw prog = new DiffuseDraw();
prog.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
When I compile and run, I only get a black screen. I am guessing that the problem is coming from the colors not changing. The number I am adding the float red blue and green by came from me wanting to diffuse a type of blue, so I took the the brightest color of blue that would appear and divided it by 290, the number of times the loop would run.

Instead of
87/290, 178/290, and 211/290,
try using
(float)87/290, (float)178/290, and (float)211/290.
That will, at least, add some color to the window- the problem is that by default, a number like 87/290 will be evaluated to 0; casting it to a float will give the desired result of 0.3 instead.