We Keep Coding

Draw Line Graph2D with data [duplicate]

In my program I want to draw a simple score line graph. I have a text file and on each line is an integer score, which I read in and want to pass as argument to my graph class. I'm having some trouble implementing the graph class and all the examples I've seen have their methods in the same class as their main, which I won't have.
I want to be able to pass my array to the object and generate a graph, but when calling my paint method it is asking me for a Graphics g... This is what I have so far:
public class Graph extends JPanel {
public void paintGraph (Graphics g){
ArrayList<Integer> scores = new ArrayList<Integer>(10);
Random r = new Random();
for (int i : scores){
i = r.nextInt(20);
System.out.println(r);
}
int y1;
int y2;
for (int i = 0; i < scores.size(); i++){
y1 = scores.get(i);
y2 = scores.get(i+1);
g.drawLine(i, y1, i+1, y2);
}
}
}
For now I have inserted a simple random number generator to fill up my array.
I have an existing frame and basically want to instantiate the Graph class and mount the panel onto my frame. I'm really sorry that this question seems so jumbled by the way, but I've had little sleep...
The code in my main statement is:
testFrame = new JFrame();
testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Graph graph = new Graph();
testFrame.add(graph);
I'm not sure exactly what an SSCE is but this is my attempt at one:
public class Test {
JFrame testFrame;
public Test() {
testFrame = new JFrame();
testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Graph graph = new Graph();
testFrame.add(graph);
testFrame.setBounds(100, 100, 764, 470);
testFrame.setVisible(true);
}
Graph.java
public class Graph extends JPanel {
public Graph() {
setSize(500, 500);
}
#Override
public void paintComponent(Graphics g) {
Graphics2D gr = (Graphics2D) g; // This is if you want to use Graphics2D
// Now do the drawing here
ArrayList<Integer> scores = new ArrayList<Integer>(10);
Random r = new Random();
for (int i : scores) {
i = r.nextInt(20);
System.out.println(r);
}
int y1;
int y2;
for (int i = 0; i < scores.size() - 1; i++) {
y1 = (scores.get(i)) * 10;
y2 = (scores.get(i + 1)) * 10;
gr.drawLine(i * 10, y1, (i + 1) * 10, y2);
}
}
}

Problems with your code and suggestions:
Again you need to change the preferredSize of the component (here the Graph JPanel), not the size
Don't set the JFrame's bounds.
Call pack() on your JFrame after adding components to it and before calling setVisible(true)
Your foreach loop won't work since the size of your ArrayList is 0 (test it to see that this is correct). Instead use a for loop going from 0 to 10.
You should not have program logic inside of your paintComponent(...) method but only painting code. So I would make the ArrayList a class variable and fill it inside of the class's constructor.
For example:
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.*;
#SuppressWarnings("serial")
public class DrawGraph extends JPanel {
private static final int MAX_SCORE = 20;
private static final int PREF_W = 800;
private static final int PREF_H = 650;
private static final int BORDER_GAP = 30;
private static final Color GRAPH_COLOR = Color.green;
private static final Color GRAPH_POINT_COLOR = new Color(150, 50, 50, 180);
private static final Stroke GRAPH_STROKE = new BasicStroke(3f);
private static final int GRAPH_POINT_WIDTH = 12;
private static final int Y_HATCH_CNT = 10;
private List<Integer> scores;
public DrawGraph(List<Integer> scores) {
this.scores = scores;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
double xScale = ((double) getWidth() - 2 * BORDER_GAP) / (scores.size() - 1);
double yScale = ((double) getHeight() - 2 * BORDER_GAP) / (MAX_SCORE - 1);
List<Point> graphPoints = new ArrayList<Point>();
for (int i = 0; i < scores.size(); i++) {
int x1 = (int) (i * xScale + BORDER_GAP);
int y1 = (int) ((MAX_SCORE - scores.get(i)) * yScale + BORDER_GAP);
graphPoints.add(new Point(x1, y1));
}
// create x and y axes
g2.drawLine(BORDER_GAP, getHeight() - BORDER_GAP, BORDER_GAP, BORDER_GAP);
g2.drawLine(BORDER_GAP, getHeight() - BORDER_GAP, getWidth() - BORDER_GAP, getHeight() - BORDER_GAP);
// create hatch marks for y axis.
for (int i = 0; i < Y_HATCH_CNT; i++) {
int x0 = BORDER_GAP;
int x1 = GRAPH_POINT_WIDTH + BORDER_GAP;
int y0 = getHeight() - (((i + 1) * (getHeight() - BORDER_GAP * 2)) / Y_HATCH_CNT + BORDER_GAP);
int y1 = y0;
g2.drawLine(x0, y0, x1, y1);
}
// and for x axis
for (int i = 0; i < scores.size() - 1; i++) {
int x0 = (i + 1) * (getWidth() - BORDER_GAP * 2) / (scores.size() - 1) + BORDER_GAP;
int x1 = x0;
int y0 = getHeight() - BORDER_GAP;
int y1 = y0 - GRAPH_POINT_WIDTH;
g2.drawLine(x0, y0, x1, y1);
}
Stroke oldStroke = g2.getStroke();
g2.setColor(GRAPH_COLOR);
g2.setStroke(GRAPH_STROKE);
for (int i = 0; i < graphPoints.size() - 1; i++) {
int x1 = graphPoints.get(i).x;
int y1 = graphPoints.get(i).y;
int x2 = graphPoints.get(i + 1).x;
int y2 = graphPoints.get(i + 1).y;
g2.drawLine(x1, y1, x2, y2);
}
g2.setStroke(oldStroke);
g2.setColor(GRAPH_POINT_COLOR);
for (int i = 0; i < graphPoints.size(); i++) {
int x = graphPoints.get(i).x - GRAPH_POINT_WIDTH / 2;
int y = graphPoints.get(i).y - GRAPH_POINT_WIDTH / 2;;
int ovalW = GRAPH_POINT_WIDTH;
int ovalH = GRAPH_POINT_WIDTH;
g2.fillOval(x, y, ovalW, ovalH);
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
private static void createAndShowGui() {
List<Integer> scores = new ArrayList<Integer>();
Random random = new Random();
int maxDataPoints = 16;
int maxScore = 20;
for (int i = 0; i < maxDataPoints ; i++) {
scores.add(random.nextInt(maxScore));
}
DrawGraph mainPanel = new DrawGraph(scores);
JFrame frame = new JFrame("DrawGraph");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Which will create a graph that looks like so:

Just complementing Hovercraft Full Of Eels's solution:
I reworked his code, tweaked it a bit, adding a grid, axis labels and now the Y-axis goes from the minimum value present up to the maximum value. I planned on adding a couple of getters/setters but I didn't need them, you can add them if you want.
Here is the Gist link, I'll also paste the code below: GraphPanel on Gist
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class GraphPanel extends JPanel {
private int width = 800;
private int heigth = 400;
private int padding = 25;
private int labelPadding = 25;
private Color lineColor = new Color(44, 102, 230, 180);
private Color pointColor = new Color(100, 100, 100, 180);
private Color gridColor = new Color(200, 200, 200, 200);
private static final Stroke GRAPH_STROKE = new BasicStroke(2f);
private int pointWidth = 4;
private int numberYDivisions = 10;
private List<Double> scores;
public GraphPanel(List<Double> scores) {
this.scores = scores;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
double xScale = ((double) getWidth() - (2 * padding) - labelPadding) / (scores.size() - 1);
double yScale = ((double) getHeight() - 2 * padding - labelPadding) / (getMaxScore() - getMinScore());
List<Point> graphPoints = new ArrayList<>();
for (int i = 0; i < scores.size(); i++) {
int x1 = (int) (i * xScale + padding + labelPadding);
int y1 = (int) ((getMaxScore() - scores.get(i)) * yScale + padding);
graphPoints.add(new Point(x1, y1));
}
// draw white background
g2.setColor(Color.WHITE);
g2.fillRect(padding + labelPadding, padding, getWidth() - (2 * padding) - labelPadding, getHeight() - 2 * padding - labelPadding);
g2.setColor(Color.BLACK);
// create hatch marks and grid lines for y axis.
for (int i = 0; i < numberYDivisions + 1; i++) {
int x0 = padding + labelPadding;
int x1 = pointWidth + padding + labelPadding;
int y0 = getHeight() - ((i * (getHeight() - padding * 2 - labelPadding)) / numberYDivisions + padding + labelPadding);
int y1 = y0;
if (scores.size() > 0) {
g2.setColor(gridColor);
g2.drawLine(padding + labelPadding + 1 + pointWidth, y0, getWidth() - padding, y1);
g2.setColor(Color.BLACK);
String yLabel = ((int) ((getMinScore() + (getMaxScore() - getMinScore()) * ((i * 1.0) / numberYDivisions)) * 100)) / 100.0 + "";
FontMetrics metrics = g2.getFontMetrics();
int labelWidth = metrics.stringWidth(yLabel);
g2.drawString(yLabel, x0 - labelWidth - 5, y0 + (metrics.getHeight() / 2) - 3);
}
g2.drawLine(x0, y0, x1, y1);
}
// and for x axis
for (int i = 0; i < scores.size(); i++) {
if (scores.size() > 1) {
int x0 = i * (getWidth() - padding * 2 - labelPadding) / (scores.size() - 1) + padding + labelPadding;
int x1 = x0;
int y0 = getHeight() - padding - labelPadding;
int y1 = y0 - pointWidth;
if ((i % ((int) ((scores.size() / 20.0)) + 1)) == 0) {
g2.setColor(gridColor);
g2.drawLine(x0, getHeight() - padding - labelPadding - 1 - pointWidth, x1, padding);
g2.setColor(Color.BLACK);
String xLabel = i + "";
FontMetrics metrics = g2.getFontMetrics();
int labelWidth = metrics.stringWidth(xLabel);
g2.drawString(xLabel, x0 - labelWidth / 2, y0 + metrics.getHeight() + 3);
}
g2.drawLine(x0, y0, x1, y1);
}
}
// create x and y axes
g2.drawLine(padding + labelPadding, getHeight() - padding - labelPadding, padding + labelPadding, padding);
g2.drawLine(padding + labelPadding, getHeight() - padding - labelPadding, getWidth() - padding, getHeight() - padding - labelPadding);
Stroke oldStroke = g2.getStroke();
g2.setColor(lineColor);
g2.setStroke(GRAPH_STROKE);
for (int i = 0; i < graphPoints.size() - 1; i++) {
int x1 = graphPoints.get(i).x;
int y1 = graphPoints.get(i).y;
int x2 = graphPoints.get(i + 1).x;
int y2 = graphPoints.get(i + 1).y;
g2.drawLine(x1, y1, x2, y2);
}
g2.setStroke(oldStroke);
g2.setColor(pointColor);
for (int i = 0; i < graphPoints.size(); i++) {
int x = graphPoints.get(i).x - pointWidth / 2;
int y = graphPoints.get(i).y - pointWidth / 2;
int ovalW = pointWidth;
int ovalH = pointWidth;
g2.fillOval(x, y, ovalW, ovalH);
}
}
// #Override
// public Dimension getPreferredSize() {
// return new Dimension(width, heigth);
// }
private double getMinScore() {
double minScore = Double.MAX_VALUE;
for (Double score : scores) {
minScore = Math.min(minScore, score);
}
return minScore;
}
private double getMaxScore() {
double maxScore = Double.MIN_VALUE;
for (Double score : scores) {
maxScore = Math.max(maxScore, score);
}
return maxScore;
}
public void setScores(List<Double> scores) {
this.scores = scores;
invalidate();
this.repaint();
}
public List<Double> getScores() {
return scores;
}
private static void createAndShowGui() {
List<Double> scores = new ArrayList<>();
Random random = new Random();
int maxDataPoints = 40;
int maxScore = 10;
for (int i = 0; i < maxDataPoints; i++) {
scores.add((double) random.nextDouble() * maxScore);
// scores.add((double) i);
}
GraphPanel mainPanel = new GraphPanel(scores);
mainPanel.setPreferredSize(new Dimension(800, 600));
JFrame frame = new JFrame("DrawGraph");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
It looks like this:

Or simply use the JFreechart library - http://www.jfree.org/jfreechart/ .

There exist many open source projects that handle all the drawing of line charts for you with a couple of lines of code. Here's how you can draw a line chart from data in a couple text (CSV) file with the XChart library. Disclaimer: I'm the lead developer of the project.
In this example, two text files exist in ./CSV/CSVChartRows/. Notice that each row in the files represents a data point to be plotted and that each file represents a different series. series1 contains x, y, and error bar data, whereas series2 contains just x and y, data.
series1.csv
1,12,1.4
2,34,1.12
3,56,1.21
4,47,1.5
series2.csv
1,56
2,34
3,12
4,26
Source Code
public class CSVChartRows {
public static void main(String[] args) throws Exception {
// import chart from a folder containing CSV files
XYChart chart = CSVImporter.getChartFromCSVDir("./CSV/CSVChartRows/", DataOrientation.Rows, 600, 400);
// Show it
new SwingWrapper(chart).displayChart();
}
}
Resulting Plot

Override the paintComponent method of your panel so you can custom draw. Like this:
#Override
public void paintComponent(Graphics g) {
Graphics2D gr = (Graphics2D) g; //this is if you want to use Graphics2D
//now do the drawing here
...
}

Hovercraft Full Of Eels' answer is very good, but i had to change it a bit in order to get it working on my program:
int y1 = (int) ((this.height - 2 * BORDER_GAP) - (values.get(i) * yScale - BORDER_GAP));
instead of
int y1 = (int) (scores.get(i) * yScale + BORDER_GAP);
because if i used his way the graphic would be upside down
(you'd see it if you used hardcoded values (e.g 1,3,5,7,9) instead of random values)

Why are JLabels being painted over higher components in a JLayeredPane?

I have a JLayeredPane that has four layers:
JPanel set as a background
Grid of JPanels each holding a JLabel
Grid of JPanels each holding several JLabels that are only set to visible if the label in the panel below is empty
A custom component that is only used to override the paintComponent() method to draw over everything below
For some reason if I change the background colour of the labels in layer 3 and then draw to layer 4, the labels in layer 3 are painted over the graphics painted in level 4. I have tried to set ignoreRepaint() on various components as well as playing around with the opacity and code structure but all to no avail.
Does anyone know how to prevent this from happening?
I won't attach the source code because the project is quite large but I've attached an example that runs as a stand alone program and demonstrates my problem when you hit the "add arrow" button.
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.border.LineBorder;
public class GraphicsTest {
#SuppressWarnings("serial")
class Painter extends JComponent {
public Painter(int x, int y) {
setBounds(0, 0, x, y);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
}
}
private static final int CELL_SIZE = 40;
private static final int NOTE_SIZE = 20;
private JFrame frame;
private static JButton test;
private static JButton clear;
private static JLayeredPane pane = new JLayeredPane();
private static JPanel back = new JPanel();
private static JPanel[][] cellPanels = new JPanel[10][10];
private static JLabel[][] cells = new JLabel[10][10];
private static JPanel[][] notePanels = new JPanel[10][10];
private static JLabel[][][] notes = new JLabel[10][10][4];
private static Painter painter;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
GraphicsTest window = new GraphicsTest();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public GraphicsTest() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setSize(600, 700);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
pane.setBounds(50, 50, 500, 500);
pane.setLayout(null);
frame.getContentPane().add(pane);
back.setBounds(0, 0, 500, 500);
back.setBackground(Color.BLACK);
pane.add(back, new Integer(100));
for (int i = 0; i < 10; i++) {
for (int k = 0; k < 10; k++) {
String text = "";
if ((i % 2) == 1 && (k % 2) == 1) text = (i + k) + "";
cellPanels[i][k] = new JPanel();
cellPanels[i][k].setBounds(k * CELL_SIZE, i * CELL_SIZE, CELL_SIZE, CELL_SIZE);
cellPanels[i][k].setBackground(Color.WHITE);
cellPanels[i][k].setBorder(new LineBorder(Color.BLACK, 1));
cells[i][k] = new JLabel(text);
cells[i][k].setBounds(0, 0, CELL_SIZE, CELL_SIZE);
cells[i][k].setOpaque(false);
cellPanels[i][k].add(cells[i][k]);
pane.add(cellPanels[i][k], new Integer(200));
}
}
boolean display;
for (int i = 0; i < 10; i++) {
for (int k = 0; k < 10; k++) {
if ((i % 2) == 0 && (k % 2) == 0) {
display = true;
} else {
display = false;
}
notePanels[i][k] = new JPanel();
notePanels[i][k].setBounds(k * CELL_SIZE, i * CELL_SIZE, CELL_SIZE, CELL_SIZE);
notePanels[i][k].setBackground(Color.WHITE);
notePanels[i][k].setBorder(new LineBorder(Color.BLACK, 1));
notePanels[i][k].setLayout(null);
for (int m = 0; m < 2; m++) {
for (int p = 0; p < 2; p++) {
notes[i][k][(m * 2) + p] = new JLabel(30 + "");
notes[i][k][(m * 2) + p].setBounds(m * NOTE_SIZE, p * NOTE_SIZE, NOTE_SIZE, NOTE_SIZE);
notes[i][k][(m * 2) + p].setOpaque(true);
notePanels[i][k].add(notes[i][k][(m * 2) + p]);
}
}
if (display) {
notePanels[i][k].setVisible(true);
} else {
notePanels[i][k].setVisible(false);
}
pane.add(notePanels[i][k], new Integer(300));
}
}
painter = new Painter(500, 500);
pane.add(painter, new Integer(400));
test = new JButton("Add Arrow");
test.setBounds(50, 600, 100, 25);
test.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
highlightNotes();
Arrow.drawArrow(painter.getGraphics(), 20, 20, 400, 400, 20, 30, 40, Color.BLACK, Color.GREEN);
}
});
frame.getContentPane().add(test);
clear = new JButton("Clear");
clear.setBounds(175, 600, 100, 25);
clear.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
painter.repaint();
}
});
frame.getContentPane().add(clear);
}
private static void highlightNotes() {
for (int i = 0; i < 10; i++) {
for (int k = 0; k < 10; k++) {
for (int n = 0; n < 4; n++) {
notes[i][k][n].setBackground(Color.BLUE);
}
}
}
}
static class Arrow {
public static void drawArrow(Graphics g, int tailx, int taily, int headx, int heady,
int shaftw, int headw, int headh, Color outline, Color fill) {
if ((shaftw % 2) == 0) {
shaftw--;
}
if ((headw % 2) == 0) {
headw--;
}
if ((headh % 2) == 0) {
headh--;
}
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
double length = Math.sqrt((double) (((headx - tailx) * (headx - tailx))
+ ((heady - taily) * (heady - taily))));
int tailLength = (int) (length - headw) + 1;
double theta = Math.atan2(heady - taily, headx - tailx);
Point point1 = new Point(0, -(shaftw / 2));
point1 = getTransPoint(point1, theta);
point1.x += tailx;
point1.y += taily;
Point point2 = new Point(tailLength, -(shaftw / 2));
point2 = getTransPoint(point2, theta);
point2.x += tailx;
point2.y += taily;
Point point3 = new Point(tailLength, -(headw / 2));
point3 = getTransPoint(point3, theta);
point3.x += tailx;
point3.y += taily;
Point point4 = new Point((int) length, 0);
point4 = getTransPoint(point4, theta);
point4.x += tailx;
point4.y += taily;
Point point5 = new Point(tailLength, (headw / 2));
point5 = getTransPoint(point5, theta);
point5.x += tailx;
point5.y += taily;
Point point6 = new Point(tailLength, (shaftw / 2));
point6 = getTransPoint(point6, theta);
point6.x += tailx;
point6.y += taily;
Point point7 = new Point(0, (shaftw / 2));
point7 = getTransPoint(point7, theta);
point7.x += tailx;
point7.y += taily;
//Create arrow at tail coordinates passed in
Polygon arrow = new Polygon();
arrow.addPoint(point1.x, point1.y);
arrow.addPoint(point2.x, point2.y);
arrow.addPoint(point3.x, point3.y);
arrow.addPoint(point4.x, point4.y);
arrow.addPoint(point5.x, point5.y);
arrow.addPoint(point6.x, point6.y);
arrow.addPoint(point7.x, point7.y);
//Draw and fill the arrow
g2.setColor(fill);
g2.fillPolygon(arrow);
g2.setColor(outline);
g2.drawPolygon(arrow);
}
private static Point getTransPoint(Point point, double theta) {
int x = (int) ((point.x * Math.cos(theta)) - (point.y * Math.sin(theta)));
int y = (int) ((point.y * Math.cos(theta)) + (point.x * Math.sin(theta)));
return new Point(x, y);
}
}
}

Determine if circles intersect

I am working on a project where I have to draw 20 circles with random starting points and random sizes. Then I have to determine if any of the circles intersect. If a circle intersects with another, I have to color that circle green. And if the circle does not intersect with another, the color needs to be red. I have all of the code... I think... but when I run it, I still get some circles that should be green, but are red instead. Here is my code. Any help will be greatly appreciated.
import java.awt.Graphics;
import javax.swing.JPanel;
import java.util.Random;
import javax.swing.JFrame;
import java.awt.*;
public class IntersectingCircles extends JPanel
{
private int[] xAxis = new int [20]; // array to hold x axis points
private int[] yAxis = new int [20]; // array to hold y axis points
private int[] radius = new int [20]; // array to hold radius length
public static void main (String[] args)
{
JFrame frame = new JFrame("Random Circles");
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add (new IntersectingCircles());
frame.pack();
frame.setVisible(true);
}
public IntersectingCircles()
{
setPreferredSize(new Dimension(1300, 800)); // set window size
Random random = new Random();
for (int i = 0; i < 20; i++)
{
xAxis[i] = random.nextInt(800) + 100;
yAxis[i] = random.nextInt(500) + 100;
radius[i] = random.nextInt(75) + 10;
}
}
public void paintComponent(Graphics g)
{
for (int i = 0; i < 20; i++)
{
int color = 0;
for (int h = 0; h < 20; h++)
{
if(i < h)
{
double x1 = 0, x2 = 0, y1 = 0, y2 = 0, d = 0;
x1 = (xAxis[i] + radius[i]);
y1 = (yAxis[i] + radius[i]);
x2 = (xAxis[h] + radius[h]);
y2 = (yAxis[h] + radius[h]);
d = (Math.sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1)*(y2 - y1))));
if (d > radius[i] + radius[h] || d < (Math.abs(radius[i] - radius[h])))
{
color = 0;
}
else
{
color = 1;
break;
}
}
}
if (color == 0)
{
g.setColor(Color.RED);
g.drawOval(xAxis[i], yAxis[i], radius[i] * 2, radius[i] * 2);
}
else
{
g.setColor(Color.GREEN);
g.drawOval(xAxis[i], yAxis[i], radius[i] * 2, radius[i] * 2);
}
}
}
}

In the inside for loop, you are only comparing circles of i index with circles with h index, but only those with i < h, because of the condition:
for (int h = 0; h < 20; h++)
{
if(i < h)
{
...
So, instead you should compare every i circle with every h circle, except if they are the same. You want instead:
for (int h = 0; h < 20; h++)
{
if(i != h) //note the change here
{
...

How to render colours properly in Java Graphics

I was using this code placed here to generate bar-charts for my datasets. However, the colours were all the same (red in the code), so I decided to generate a colour ramp for this. I wrote the following code:
Color[] getColorRamp(int numColours)
{
Color[] colours = new Color[numColours];
int red_1 = 255;
int green_1 = 0;
int blue_1 = 0;
int red_2 = 0;
int green_2 = 0;
int blue_2 = 255;
int count = 0;
for (float t=0.0f;t<1.0f;t+=1.0/(float)numColours) {
colours[count] = new Color((int)(t*red_2 + (1-t)*red_1),
(int)(t*green_2 + (1-t)*green_1),
(int)(t*blue_2 + (1-t)*blue_1),34);
//System.out.print((int)(t*red_2 + (1-t)*red_1) +",");
//System.out.print((int)(t*green_2 + (1-t)*green_1) +",");
//System.out.println((int)(t*blue_2 + (1-t)*blue_1));
}
return colours;
}
It is here, where the problem starts. Only the first colour (pretty light blue) get rendered properly. Other colours are rendered as black! You can see that I have put System.out.println to verify the colours generated (commented in the code posted here). I saw that colours were generated as perfect RGB combinations.
The modified barchart function is posted here:
void drawBarChart(Graphics g, double[] values, String[] names, String title)
{
if (values == null || values.length == 0)
return;
double minValue = 0;
double maxValue = 0;
for (int i = 0; i < values.length; i++) {
if (minValue > values[i])
minValue = values[i];
if (maxValue < values[i])
maxValue = values[i];
}
//Graphics2D g = (Graphics2D)gg;
Dimension d = getSize();
int clientWidth = d.width;
int clientHeight = d.height;
int barWidth = clientWidth / values.length;
Font titleFont = new Font("SansSerif", Font.BOLD, 20);
FontMetrics titleFontMetrics = g.getFontMetrics(titleFont);
Font labelFont = new Font("SansSerif", Font.PLAIN, 10);
FontMetrics labelFontMetrics = g.getFontMetrics(labelFont);
int titleWidth = titleFontMetrics.stringWidth(title);
int y = titleFontMetrics.getAscent();
int x = (clientWidth - titleWidth) / 2;
g.setFont(titleFont);
g.drawString(title, x, y);
int top = titleFontMetrics.getHeight();
int bottom = labelFontMetrics.getHeight();
if (maxValue == minValue)
return;
double scale = (clientHeight - top - bottom) / (maxValue - minValue);
y = clientHeight - labelFontMetrics.getDescent();
g.setFont(labelFont);
Color[] colours = getColorRamp(values.length);
for (int i = 0; i < values.length; i++) {
int valueX = i * barWidth + 1;
int valueY = top;
int height = (int) (values[i] * scale);
if (values[i] >= 0)
valueY += (int) ((maxValue - values[i]) * scale);
else {
valueY += (int) (maxValue * scale);
height = -height;
}
g.setColor(colours[i]);
g.fillRect(valueX, valueY, barWidth - 2, height);
g.setColor(Color.black);
g.drawRect(valueX, valueY, barWidth - 2, height);
int labelWidth = labelFontMetrics.stringWidth(names[i]);
x = i * barWidth + (barWidth - labelWidth) / 2;
g.drawString(names[i], x, y);
}
//paintComponent(g);
}
I wish to know, what mistake I am making!

You're probably going to hit yourself on the head now. The reason it fails is that you forget to increase the variable count after setting the first colour, so you're constantly overwriting the first element of the Color array, and leaving all the other values in the array as their initial default (null).
Fixed code:
for (float t=0.0f;t<1.0f;t+=1.0/(float)numColours) {
colours[count++] = new Color((int)(t*red_2 + (1-t)*red_1),
(int)(t*green_2 + (1-t)*green_1),
(int)(t*blue_2 + (1-t)*blue_1),34);
}
(Notice the colours[count++])

How do I draw rectangles in jpanel based on calculated averages

I have a gui where data is entered and the averages are calculated for 5 different sets of data. These are stored in an array with the five averages in the five positions.
How do I make it draw rectangles in a jpanel to look like a graph of those 5 averages ?

..make it draw rectangles in a jpanel to look like a graph...
Assuming, youre talking about bar graph,
Have a look at this example :
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class SimpleBarChart extends JPanel {
private double[] value;
private String[] languages;
private String title;
public SimpleBarChart(double[] val, String[] lang, String t) {
languages = lang;
value = val;
title = t;
}
#Override
public void paintComponent(Graphics graphics) {
super.paintComponent(graphics);
if (value == null || value.length == 0) {
return;
}
double minValue = 0;
double maxValue = 0;
for (int i = 0; i < value.length; i++) {
if (minValue > value[i]) {
minValue = value[i];
}
if (maxValue < value[i]) {
maxValue = value[i];
}
}
Dimension dim = getSize();
int clientWidth = dim.width;
int clientHeight = dim.height;
int barWidth = clientWidth / value.length;
Font titleFont = new Font("Book Antiqua", Font.BOLD, 15);
FontMetrics titleFontMetrics = graphics.getFontMetrics(titleFont);
Font labelFont = new Font("Book Antiqua", Font.PLAIN, 10);
FontMetrics labelFontMetrics = graphics.getFontMetrics(labelFont);
int titleWidth = titleFontMetrics.stringWidth(title);
int q = titleFontMetrics.getAscent();
int p = (clientWidth - titleWidth) / 2;
graphics.setFont(titleFont);
graphics.drawString(title, p, q);
int top = titleFontMetrics.getHeight();
int bottom = labelFontMetrics.getHeight();
if (maxValue == minValue) {
return;
}
double scale = (clientHeight - top - bottom) / (maxValue - minValue);
q = clientHeight - labelFontMetrics.getDescent();
graphics.setFont(labelFont);
for (int j = 0; j < value.length; j++) {
int valueP = j * barWidth + 1;
int valueQ = top;
int height = (int) (value[j] * scale);
if (value[j] >= 0) {
valueQ += (int) ((maxValue - value[j]) * scale);
} else {
valueQ += (int) (maxValue * scale);
height = -height;
}
graphics.setColor(Color.blue);
graphics.fillRect(valueP, valueQ, barWidth - 2, height);
graphics.setColor(Color.black);
graphics.drawRect(valueP, valueQ, barWidth - 2, height);
int labelWidth = labelFontMetrics.stringWidth(languages[j]);
p = j * barWidth + (barWidth - labelWidth) / 2;
graphics.drawString(languages[j], p, q);
}
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(350, 300);
double[] value = new double[5];
String[] languages = new String[5];
value[0] = 1;
languages[0] = "Visual Basic";
value[1] = 2;
languages[1] = "PHP";
value[2] = 3;
languages[2] = "C++";
value[3] = 4;
languages[3] = "C";
value[4] = 5;
languages[4] = "Java";
frame.getContentPane().add(new SimpleBarChart(value, languages,
"Programming Languages"));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
Also see JFreeChart and if you dont mind using an external library.
Example that you might need via #trashGod : example and its source code.