Develop Reference

How to get multiple rectangles in one larger one

Im trying to display the maximum number of smaller rectangles that will fit into a larger one. I can get the horizontal rectangles to show up, but the vertical rectangles will not show up. I need help on figuring out how to get the vertical rectangles to display in the JFrame.
Here is the class with the main:
import javax.swing.*;
public class MyPanel extends JComponent {
public static void main(String[] arguments) {
LargeRec large = new LargeRec();
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("Rectangle");
frame.setResizable(false);
frame.setVisible(true);
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setSize(500,400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(large);
}
}
This is the class for creating the rectangle's:
import javax.swing.*;
import java.awt.*;
public class LargeRec extends JComponent {
static int larX;
static int larY;
static int smaX;
static int smaY;
public static int getRandomIntRange(int min, int max) {
int x = (int) (Math.random() * ((max + 1 - min))) + min;
if (x > (max + 1))
x = max;
return x;
}
public void paint(Graphics g) {
larX = getRandomIntRange(100, 300);
larY = getRandomIntRange(100, 300);
while (larX == larY) {
larX = getRandomIntRange(100, 300);
larY = getRandomIntRange(100, 300);
}
while (larY > larX) {
larX = getRandomIntRange(100, 300);
larY = getRandomIntRange(100, 300);
}
smaX = getRandomIntRange(10, 50);
smaY = getRandomIntRange(10, 50);
while (smaX == smaY) {
smaX = getRandomIntRange(10, 50);
smaY = getRandomIntRange(10, 50);
}
while (smaY > smaX) {
smaX = getRandomIntRange(10, 50);
smaY = getRandomIntRange(10, 50);
}
g.drawRect(0, 0, larX, larY);
g.setColor(Color.black);
g.fillRect(0, 0, larX, larY);
int LX = larX;
int LY = larY;
int SX = smaX;
int SY = smaY;
for (int nx = 0; nx <= larX; nx = nx + smaX) {
while (LY >= SY) {
LY = LY - SY;
if(LX>=SX) {
g.setColor(Color.red);
g.drawRect(nx, LY, smaX, smaY);
}
}
LX = LX - SX;
LY = larY;
}
Graphics2D g2 = (Graphics2D) g;
for (int ny =LX; ny+smaY <=LX ; ny = ny + smaY) {
while (LY >= SX) {
g2.setColor(Color.blue);
g2.drawRect(ny, LY, smaY, smaX);
LY = LY - SX;
}
LY=larY;
}
}
}
It should output a black rectangle with smaller horizontal rectangles and vertical rectangles. It displays the horizontal (red) rectangles, but not the vertical(blue) rectangles.
Here is an example of a bad output:

Java - Hexagon location in grid

Im searching for an algorythem to get the location of a hexagon in a grid.
I found this one but it doesnt seam to work:
for(int i = 0; i < width; i++) {
for(int j = 0; j < height; j++) {
grid[i][j] = new Hexagon(x+(j*((3*Hexagon.S)/2)), y+((j%2)*Hexagon.A)+(2*i*Hexagon.A));
}
}
The output is kind of strange:
output
This is the window-creating class(just a test class):
import java.awt.Container;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Grid extends JPanel {
private static final long serialVersionUID = 1L;
public static void main(String[] args) {
int width = 2;
int height = 4;
int x = 100;
int y = 100;
Hexagon[][] grid = new Hexagon[width][height];
JFrame f = new JFrame();
Container cp = f.getContentPane();
for(int i = 0; i < width; i++) {
for(int j = 0; j < height; j++) {
grid[i][j] = new Hexagon(x+(j*((3*Hexagon.S)/2)), y+((j%2)*Hexagon.A)+(2*i*Hexagon.A));
cp.add(grid[i][j]);
}
}
f.setLayout(null);
f.setBounds(100, 100, 300, 300);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
}
The Hexagon.java class:
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Polygon;
import javax.swing.JButton;
public class Hexagon extends JButton {
public static final int S = 50;
public static final int A = (int) (Math.sqrt(3)*(S/2));
private static final long serialVersionUID = 1L;
private final int x, y;
private final Polygon shape;
public Hexagon(int x, int y) {
this.x = x;
this.y = y;
this.shape = initHexagon();
setSize(2*S, 2*A);
setLocation(x-S, y-A);
setContentAreaFilled(false);
}
private Polygon initHexagon() {
Polygon p = new Polygon();
p.addPoint(x+(S/2), y-A);
p.addPoint(x+S, y);
p.addPoint(x+(S/2), y+A);
p.addPoint(x-(S/2), y+A);
p.addPoint(x-S, y);
p.addPoint(x-(S/2), y-A);
return p;
}
protected void paintComponent(Graphics g) {
g.setColor(Color.BLACK);
g.drawPolygon(this.shape);
}
protected void paintBorder(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLACK);
g2.setStroke(new BasicStroke(4));
g2.drawPolygon(this.shape);
}
public boolean contains(int x, int y) {
return this.shape.contains(x, y);
}
}
As i said, this class worked just fine using non-rectangular shapes.
There was no clipping or such.

You've posted your definition of Hexagon too late, so I copy-pasted a modified version of a similar class from my collection of code snippets.
Here is one way to generate a hexagonal grid:
import java.awt.Container;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JComponent;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Color;
import java.awt.GridLayout;
import java.util.function.*;
public class Hexagons extends JPanel {
private static final long serialVersionUID = 1L;
/** Height of an equilateral triangle with side length = 1 */
private static final double H = Math.sqrt(3) / 2;
static class Hexagon {
final int row;
final int col;
final double sideLength;
public Hexagon(int r, int c, double a) {
this.row = r;
this.col = c;
this.sideLength = a;
}
double getCenterX() {
return 2 * H * sideLength * (col + (row % 2) * 0.5);
}
double getCenterY() {
return 3 * sideLength / 2 * row;
}
void foreachVertex(BiConsumer<Double, Double> f) {
double cx = getCenterX();
double cy = getCenterY();
f.accept(cx + 0, cy + sideLength);
f.accept(cx - H * sideLength, cy + 0.5 * sideLength);
f.accept(cx - H * sideLength, cy - 0.5 * sideLength);
f.accept(cx + 0, cy - sideLength);
f.accept(cx + H * sideLength, cy - 0.5 * sideLength);
f.accept(cx + H * sideLength, cy + 0.5 * sideLength);
}
}
public static void main(String[] args) {
final int width = 50;
final int height = 50;
final Hexagon[][] grid = new Hexagon[height][width];
for(int row = 0; row < height; row++) {
for(int col = 0; col < width; col++) {
grid[row][col] = new Hexagon(row, col, 50);
}
}
JFrame f = new JFrame("Hexagons");
f.getContentPane().setLayout(new GridLayout());
f.getContentPane().add(new JComponent() {
#Override public void paint(Graphics g) {
g.setColor(new Color(0xFF, 0xFF, 0xFF));
g.fillRect(0,0,1000,1000);
g.setColor(new Color(0,0,0));
final int[] xs = new int[6];
final int[] ys = new int[6];
for (Hexagon[] row : grid) {
for (Hexagon h: row) {
final int[] i = {0};
h.foreachVertex((x, y) -> {
xs[i[0]] = (int)((double)x);
ys[i[0]] = (int)((double)y);
i[0]++;
});
g.drawPolygon(xs, ys, 6);
g.drawString(
"(" + h.row + "," + h.col + ")",
(int)(h.getCenterX() - 15),
(int)(h.getCenterY() + 12)
);
}
}
}
});
f.setBounds(0, 0, 500, 500);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
try {
Thread.sleep(100);
} catch (Throwable e) {
} finally {
f.repaint();
}
}
}
It produces the following output:
Sorry for the lack of anti-aliasing. A few hints:
Height H of an equilateral triangle with unit side length is sqrt(3) / 2
The six offsets from the center are (0, +1), (H, +1/2), (H, -1/2), (0, -1), (-H, -1/2), (-H, +1/2), everything times side length.
Distance between rows is 1.5, distance between columns is 2 * H (times scaling constant = side length).
Every odd row is shifted by (0, H) (times scaling constant).
The position of (row,col)-th hexagon is (1.5 * row, 2 * H * (col + 0.5 * (row % 2))) (times constant).
If you want to rotate the hexagons such that two of their sides are horizontal, you have to flip rows and columns.

Nesting parabolic curves from straight lines

I am having trouble replicating the picture for my assignment. I would appreciate any tips or solutions. I believe I have the general idea down, but I am having a hard time figuring out the math to replicate the image and doing everything in a single loop.
My program needs to meet these criteria:
Match the Image
Generate a random color for each pair of parabolic curve
Work with any width or height
Use a single loop to draw the entire figure.
Here is the image:
This is what I have tried so far
public static final int WIDTH = 500;
public static final int HEIGHT = 500;
public static final int LINE_INCREMENT = 5;
public static void main(String[] args) {
DrawingPanel panel = new DrawingPanel(WIDTH, HEIGHT);
Graphics g = panel.getGraphics();
int d = 0;
int iterations = HEIGHT/LINE_INCREMENT;
Random rand = new Random();
int red = 0, green = 0, blue = 0;
red = rand.nextInt(128) + 128;
green = rand.nextInt(128) + 128;
blue = rand.nextInt(128) + 128;
g.setColor(new Color(red,green,blue));
for(int y = 0; y < iterations; y++) {
g.drawLine(0, d, d, HEIGHT);
g.drawLine(WIDTH, d, d, 0);
d += LINE_INCREMENT;
}
red = rand.nextInt(128) + 128;
green = rand.nextInt(128) + 128;
blue = rand.nextInt(128) + 128;
g.setColor(new Color(red,green,blue));
d = 0;
for (int x = 0; x < iterations/2; x++) {
g.drawLine(WIDTH/4, d + HEIGHT/4, d + WIDTH/4, HEIGHT - HEIGHT/4);
g.drawLine(d + WIDTH/4, WIDTH/4, WIDTH - WIDTH/4, d + WIDTH/4);
d += LINE_INCREMENT;
}
}
The output:

The way to implement it is by overriding paintComponent:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class ParabolicCurves extends JFrame {
private static final int SIZE = 600;
private static final int LINE_INCREMENT = 5;
private static final int NUM_OF_PATTERNS = 4;
private Random rand = new Random();
ParabolicCurves() {
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
JPanel panel = new DrawingPanel(SIZE);
add(panel, BorderLayout.CENTER);
pack();
setVisible(true);
}
class DrawingPanel extends JPanel{
public DrawingPanel(int size) {
setPreferredSize(new Dimension(size, size));
setBackground(Color.WHITE);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
int red, green, blue, delta , iterations;
int height, width ,startX, startY, endX, endY ;
Rectangle boundingRrectangle = getBounds();
for(int pattern = 0 ; pattern < NUM_OF_PATTERNS; pattern++) {
red = rand.nextInt(128) + 128;
green = rand.nextInt(128) + 128;
blue = rand.nextInt(128) + 128;
g.setColor(new Color(red,green,blue));
height = (int) boundingRrectangle.getHeight();
width = (int) boundingRrectangle.getWidth();
startX = (int) boundingRrectangle.getX();
startY = (int) boundingRrectangle.getY();
endX = startX+width;
endY = startY+ height;
iterations = Math.min(width, height)/LINE_INCREMENT;
delta = 0;
for (int x = 0; x < iterations ; x++) {
g.drawLine(startX, startY+delta, startX+delta, endY);
g.drawLine(endX, startY+delta, startX+delta, startY);
delta += LINE_INCREMENT;
}
//change bounding rectangle
boundingRrectangle = new Rectangle(startX+(width/4),
startY+(width/4), width/2, height/2);
}
}
}
public static void main(String[] args) {
new ParabolicCurves();
}
}
Output:

Java drawImage() not drawing

Within my program, I have the following code:
package io.github.AdmiralSbs.DiceWars;
import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.Scanner;
public class HexDisplay extends JPanel {
private static final long serialVersionUID = 1L;
public static final int SIZE = 200;
private int height;
private int width;
private Hex[][] hex;
private BufferedImage myImage;
private Graphics drawer;
public HexDisplay(File f) throws IOException {
Scanner key = new Scanner(f);
int[] temp = commaSplit(key.nextLine());
height = temp[0];
width = temp[1];
hex = new Hex[width][height];
for (int w = 0; w < width; w++) {
for (int h = 0; h < height; h++) {
//temp = commaSplit(key.nextLine());
if (h % 2 == 0)
hex[w][h] = new Hex((int) (SIZE * (w + 0.5)),
(int) (SIZE * (h + 0.5)), SIZE);
else
hex[w][h] = new Hex((int) (SIZE * (w + 1.5)),
(int) (SIZE * (h + 0.5)), SIZE);
System.out.println(hex[w][h].getX() + " " + hex[w][h].getY());
}
}
key.close();
starting();
ImageIO.write(myImage, "jpg", new File("outPic.jpg"));
}
public void starting() {
setPreferredSize(new Dimension(400,400));
setLayout(new FlowLayout());
myImage = new BufferedImage(400, 400, BufferedImage.TYPE_INT_RGB);
drawer = myImage.getGraphics();
drawer.setColor(Color.BLUE);
drawer.fillRect(0, 0, 400, 400);
drawStuff(drawer);
repaint();
}
public int[] commaSplit(String s) {
String[] str = s.split(",");
int[] ret = new int[str.length];
for (int i = 0; i < str.length; i++) {
ret[i] = Integer.parseInt(str[i]);
}
return ret;
}
public void paintComponents(Graphics g) {
g.drawImage(myImage, 0, 0, this);
System.out.println("Painted");
}
public void drawStuff(Graphics g) {
for (int w = 0; w < width; w++) {
for (int h = 0; h < height; h++) {
hex[w][h].draw(g);
}
}
System.out.println("Drew");
revalidate();
repaint();
paintComponents(g);
}
}
What I would expect to happen is for the frame that contains this JPanel to display the image, but it does not. All System.out.println() methods are called as expected, and I am able to save the image as a .jpg file. However, the image is not displayed in the GUI. What can be done?

You have a typo:
// v
public void paintComponents(Graphics g) {
It should be paintComponent.
And should contain a call to super method:
super.paintComponent(g);
as the first line in the method

Java: Draw a circular spiral using drawArc

I'm working on a java programming exercise where we have to draw a circular spiral using the drawArc method so that the result looks similar to this:
I've been working on this for a while and this is what I have so far:
import java.awt.Graphics;
import javax.swing.JPanel;
import javax.swing.JFrame;
public class CircSpiral extends JPanel {
public void paintComponent(Graphics g) {
int x = 100;
int y = 120;
int width = 40;
int height = 60;
int startAngle = 20;
int arcAngle = 80;
for (int i = 0; i < 5; i++) {
g.drawArc(x, y, width, height, startAngle, arcAngle);
g.drawArc(x + 10, y + 10, width, height, startAngle + 10, arcAngle);
x = x + 5;
y = y + 5;
startAngle = startAngle - 10;
arcAngle = arcAngle + 10;
}
}
public static void main(String[] args) {
CircSpiral panel = new CircSpiral();
JFrame application = new JFrame();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.add(panel);
application.setSize(300, 300);
application.setVisible(true);
}
}
My code gives me this result:
I know the problem lies in my arguments for the drawArc method because the numbers aren't right, but I don't know how to go about making the numbers go in a circular manner. Any help is appreciated. Thank you!

Your idea is almost right. I did some modifications. You need to inverse the angle to draw the other side of the spiral and use fixed point to startAngle.
import java.awt.Graphics;
import javax.swing.JPanel;
import javax.swing.JFrame;
public class CircSpiral extends JPanel {
public void paintComponent(Graphics g) {
int x = getSize().width / 2 - 10;
int y = getSize().height/ 2 - 10;
int width = 20;
int height = 20;
int startAngle = 0;
int arcAngle = 180;
int depth = 10;
for (int i = 0; i < 10; i++) {
if (i % 2 == 0) {
// g.drawArc(x + 10, y + 10, width, height, startAngle + 10, -arcAngle);
// x = x - 5;
y = y - depth;
width = width + 2 * depth;
height = height + 2 * depth;
g.drawArc(x, y, width, height, startAngle, -arcAngle);
} else {
// g.drawArc(x + 10, y + 10, width, height, startAngle + 10, arcAngle);
x = x - 2 * depth;
y = y - depth;
width = width + 2 * depth;
height = height + 2 * depth;
g.drawArc(x, y, width, height, startAngle, arcAngle);
}
}
}
public static void main(String[] args) {
CircSpiral panel = new CircSpiral();
JFrame application = new JFrame();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.add(panel);
application.setSize(300, 300);
application.setVisible(true);
}
}

If this were my project, yes I'd draw my arcs in a loop, but within the loop, I'd try to make the arc's bounding box bigger but still centered over the same location. To do this I'd decrement x and y by some small constant, say DELTA (which I'd set to == 1), and I'd increment width and height by 2 * DELTA. I'd also leave my arcAngle unchanged but rather would change my startAngle in the loop like so: startAngle = startAngle - arcAngle;.
For example, this:
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JPanel;
import javax.swing.JFrame;
#SuppressWarnings("serial")
public class CircSpiral extends JPanel {
private static final int DELTA = 1;
private static final int ARC_ANGLE = 20;
private static final int PREF_W = 300;
private static final int PREF_H = PREF_W;
private static final int LOOP_MAX = 400;
public void paintComponent(Graphics g) {
int x = PREF_W / 2;
int y = PREF_H / 2;
int width = 1;
int height = 1;
int startAngle = 0;
int arcAngle = ARC_ANGLE;
for (int i = 0; i < LOOP_MAX; i++) {
g.drawArc(x, y, width, height, startAngle, arcAngle);
x = x - DELTA;
y = y - DELTA;
width += 2 * DELTA;
height += 2 * DELTA;
startAngle = startAngle - arcAngle;
}
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
public static void main(String[] args) {
CircSpiral panel = new CircSpiral();
JFrame application = new JFrame();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.add(panel);
application.pack();
application.setLocationRelativeTo(null);
application.setVisible(true);
}
}
Would result in this:

The following code will output this image:
import java.awt.Graphics;
import javax.swing.JPanel;
import javax.swing.JFrame;
public class CircSpiral extends JPanel {
public void paintComponent(Graphics g) {
int centerX = getWidth() / 2;
int centerY = getHeight() / 2;
int numIterations = 5;
int arcWidth = 10;
int arcGrowDelta = 30;
for (int i = 0; i < numIterations; i++) {
g.drawArc(centerX - arcWidth, centerY - arcWidth, 2 * arcWidth, 2 * arcWidth, 0, 180);
arcWidth += arcGrowDelta;
g.drawArc(centerX - arcWidth, centerY - arcWidth, 2 * arcWidth - arcGrowDelta, 2 * arcWidth, 180, 180);
}
}
public static void main(String[] args) {
CircSpiral panel = new CircSpiral();
JFrame application = new JFrame();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.add(panel);
application.setSize(300, 300);
application.setVisible(true);
}
}
The idea is very simple, just draw the upper half of a circle, like this:
Then increment the arc size by a constant factor and draw the bottom half of the circle but making the end point of this circle and the upper circle match, for it, just substrate the arcGrowDelta from the bottom circle width:
And repeat.

This is my solution:
package mainpack;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JPanel;
public class SpiralPanel extends JPanel {
private static final long serialVersionUID = 1L;
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
int width = 10;
int height = 10;
int startAngle = 0;
int arcAngle = 180;
int x = (getWidth() - width) / 2;
int y = (getHeight() - height) / 2;
int i = 0;
int t = 0;
while (i < 36) {
g2d.drawArc(x + t, y, width, height, startAngle, arcAngle);
if (i % 2 == 0) {
t -= 10;
}
y -= 5;
width += 10;
height += 10;
startAngle += 180;
i++;
}
}
}

I am a beginner to java and finally managed how to create the spiral.
Here is my code:
int lineLength = 20; //starting line length
int x = getWidth() / 2; //start drawing from center of JPanel
int y = getHeight() / 2; //start drawing from center of JPanel
for( int counter = 0; counter < 10; counter++ )
{
g.drawArc( x, y, lineLength, lineLength, 0, 180 ); //draws top semicircle of equal width and height
lineLength += 20; //increases arc diameter
x -= 20; //moves x coordinate left
g.drawArc( x, y - 10, lineLength, lineLength, 0, -180 ); //draws bottom semicircle; 'y - 10' joins the 2 semicircles
lineLength += 20; //increases arc diameter
y -= 20; //moves y coordinate up
}

If you're willing to let some good old trigonometry do the work, you could use this:
import java.awt. *;
import javax.swing. *;
import java.math.*;
public class Spiral extends JFrame {
public Spiral()
{
// Set Window
setTitle("Spirale");
setSize(1500, 1500);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setVisible(true);
}
public void paint(Graphics g)
{
super.paint(g);
for(double i = 1; i < 50000; i++)
{
int locY = 600 - (int) (Math.cos((Math.PI*i)/1800)*i/50);
int locX = 600 - (int) (Math.sin((Math.PI*i)/1800)*i/50);
g.drawLine(locX, locY, locX, locY);
}
}
public static void main(String[] args) {
new Spiral();
}
}