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  1. import javax.swing.*;
  2. import java.awt.*;
  3. import java.awt.event.*;
  4. import java.util.function.DoubleUnaryOperator;
  5.  
  6. public class Main extends JFrame {
  7.     private JComboBox<String> typeBox;
  8.     private JTextField equationField;
  9.     private JButton plotButton;
  10.     private GraphPanel graphPanel;
  11.  
  12.     public Main() {
  13.         setTitle("Equation Plotter");
  14.         setSize(800, 600);
  15.         setDefaultCloseOperation(EXIT_ON_CLOSE);
  16.         setLayout(new BorderLayout());
  17.  
  18.         // --- Top Panel ---
  19.         JPanel topPanel = new JPanel();
  20.         topPanel.add(new JLabel("Equation Type:"));
  21.         typeBox = new JComboBox<>(new String[]{
  22.                 "Linear", "Quadratic", "Trigonometric", "Exponential", "Custom"
  23.         });
  24.         topPanel.add(typeBox);
  25.  
  26.         topPanel.add(new JLabel("Equation (use x):"));
  27.         equationField = new JTextField("y = 2*x + 3", 20);
  28.         topPanel.add(equationField);
  29.  
  30.         plotButton = new JButton("Plot");
  31.         topPanel.add(plotButton);
  32.  
  33.         add(topPanel, BorderLayout.NORTH);
  34.  
  35.         // --- Graph Panel ---
  36.         graphPanel = new GraphPanel();
  37.         add(graphPanel, BorderLayout.CENTER);
  38.  
  39.         // --- Button Action ---
  40.         plotButton.addActionListener(e -> {
  41.             String eq = equationField.getText().replace("y=", "").replace(" ", "");
  42.             graphPanel.setEquation(parseEquation(eq));
  43.             graphPanel.repaint();
  44.         });
  45.     }
  46.  
  47.     // --- Parse equation into a function ---
  48.     private DoubleUnaryOperator parseEquation(String eq) {
  49.         try {
  50.             if (eq.contains("sin")) {
  51.                 return x -> Math.sin(evalReplace(eq, x));
  52.             } else if (eq.contains("cos")) {
  53.                 return x -> Math.cos(evalReplace(eq, x));
  54.             } else if (eq.contains("tan")) {
  55.                 return x -> Math.tan(evalReplace(eq, x));
  56.             } else {
  57.                 return x -> evalReplace(eq, x);
  58.             }
  59.         } catch (Exception e) {
  60.             JOptionPane.showMessageDialog(this, "Invalid Equation!", "Error", JOptionPane.ERROR_MESSAGE);
  61.             return x -> 0;
  62.         }
  63.     }
  64.  
  65.     // --- Evaluate expression safely ---
  66.     private double evalReplace(String eq, double x) {
  67.         try {
  68.             String replaced = eq.replace("x", "(" + x + ")");
  69.             return ((Number) new javax.script.ScriptEngineManager()
  70.                     .getEngineByName("JavaScript")
  71.                     .eval(replaced)).doubleValue();
  72.         } catch (Exception e) {
  73.             return 0;
  74.         }
  75.     }
  76.  
  77.     // --- Graph Panel Class ---
  78.     class GraphPanel extends JPanel {
  79.         private DoubleUnaryOperator function = x -> 0;
  80.  
  81.         void setEquation(DoubleUnaryOperator func) {
  82.             this.function = func;
  83.         }
  84.  
  85.         protected void paintComponent(Graphics g) {
  86.             super.paintComponent(g);
  87.             Graphics2D g2 = (Graphics2D) g;
  88.  
  89.             int w = getWidth();
  90.             int h = getHeight();
  91.  
  92.             g2.setColor(Color.WHITE);
  93.             g2.fillRect(0, 0, w, h);
  94.  
  95.             g2.setColor(Color.LIGHT_GRAY);
  96.             for (int i = 0; i < w; i += 20)
  97.                 g2.drawLine(i, 0, i, h);
  98.             for (int j = 0; j < h; j += 20)
  99.                 g2.drawLine(0, j, w, j);
  100.  
  101.             g2.setColor(Color.BLACK);
  102.             g2.setStroke(new BasicStroke(2));
  103.             g2.drawLine(0, h / 2, w, h / 2); // X-axis
  104.             g2.drawLine(w / 2, 0, w / 2, h); // Y-axis
  105.  
  106.             g2.setColor(Color.RED);
  107.             double scale = 40; // pixels per unit
  108.  
  109.             for (int i = 1; i < w; i++) {
  110.                 double x1 = (i - w / 2.0) / scale;
  111.                 double x2 = (i + 1 - w / 2.0) / scale;
  112.                 double y1 = function.applyAsDouble(x1);
  113.                 double y2 = function.applyAsDouble(x2);
  114.  
  115.                 int px1 = i;
  116.                 int py1 = (int) (h / 2 - y1 * scale);
  117.                 int px2 = i + 1;
  118.                 int py2 = (int) (h / 2 - y2 * scale);
  119.  
  120.                 g2.drawLine(px1, py1, px2, py2);
  121.             }
  122.         }
  123.     }
  124.  
  125.     public static void main(String[] args) {
  126.         SwingUtilities.invokeLater(() -> new Main().setVisible(true));
  127.     }
  128. }
Success #stdin #stdout #stderr 0.28s 67208KB
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Exception in thread "AWT-EventQueue-0" java.awt.HeadlessException: 
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
	at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:197)
	at java.desktop/java.awt.Window.<init>(Window.java:538)
	at java.desktop/java.awt.Frame.<init>(Frame.java:423)
	at java.desktop/java.awt.Frame.<init>(Frame.java:388)
	at java.desktop/javax.swing.JFrame.<init>(JFrame.java:180)
	at Main.<init>(Main.java:12)
	at Main.lambda$main$6(Main.java:126)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:389)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
https://ideone.com/Efgpn7
language:
Java (HotSpot 12)
created:
1 day ago
visibility:
public

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