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  1. import javax.swing.*;
  2. import java.awt.*;
  3. import java.awt.event.MouseAdapter;
  4. import java.awt.event.MouseEvent;
  5. import java.util.ArrayList;
  6.  
  7. public class PaintLine extends JFrame {
  8.  
  9.     private int lineLimit;
  10.     private ArrayList<StraightLine> straightLines;
  11.     private boolean isNewClick;
  12.     private StraightLine tmpStraightLine;
  13.     private boolean canDraw;
  14.  
  15.     private DrawingPanel drawingPanel;
  16.  
  17.     public static void main(String[] args) {
  18.         SwingUtilities.invokeLater(() -> {
  19.             PaintLine paintLine = new PaintLine("直線の描画");
  20.             paintLine.setVisible(true);
  21.         });
  22.     }
  23.  
  24.     PaintLine(String title) {
  25.         lineLimit = 10;
  26.         straightLines = new ArrayList<>();
  27.         isNewClick = true;
  28.         canDraw = true;
  29.  
  30.         setTitle(title);
  31.         setSize(300, 200);
  32.         setLocationRelativeTo(null);
  33.         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  34.  
  35.         drawingPanel = new DrawingPanel();
  36.  
  37.         getContentPane().add(drawingPanel);
  38.     }
  39.  
  40.     public MouseAdapter mouseAdapter = new MouseAdapter() {
  41.         @Override
  42.         public void mousePressed(MouseEvent e) {
  43.             if (canDraw) {
  44.                 if (isNewClick) {
  45.                     tmpStraightLine = new StraightLine();
  46.                     tmpStraightLine.setStartPoint(e.getPoint());
  47.                     isNewClick = false;
  48.                 } else {
  49.                     tmpStraightLine.setEndPoint(e.getPoint());
  50.                     straightLines.add(tmpStraightLine);
  51.                     tmpStraightLine = null;
  52.                     isNewClick = true;
  53.                     drawingPanel.repaint();
  54.                 }
  55.                 updateCanDrawState();
  56.             }
  57.         }
  58.     };
  59.  
  60.     public void updateCanDrawState() {
  61.         if ((straightLines != null && straightLines.isEmpty()) || straightLines.size() < lineLimit) {
  62.             canDraw = true;
  63.         } else {
  64.             canDraw = false;
  65.         }
  66.     }
  67.  
  68.     private class DrawingPanel extends JPanel {
  69.  
  70.         public DrawingPanel() {
  71.             setBackground(Color.YELLOW);
  72.             addMouseListener(mouseAdapter);
  73.         }
  74.  
  75.         protected void paintComponent(Graphics g) {
  76.             super.paintComponent(g);
  77.             Graphics2D g2d = (Graphics2D) g.create();
  78.             g2d.setColor(Color.BLUE);
  79.             if (!canDraw) {
  80.                 // straightLines.remove(straightLines.size() - 1);
  81.                 g2d.drawString("もう書けません！", 50, 50);
  82.             }
  83.             straightLines.stream().forEach(straightLine -> g2d.drawLine(
  84.                     straightLine.startPoint.x,
  85.                     straightLine.startPoint.y,
  86.                     straightLine.endPoint.x,
  87.                     straightLine.endPoint.y
  88.             ));
  89.             g2d.dispose();
  90.         }
  91.     }
  92.  
  93.     private class StraightLine {
  94.  
  95.         private Point startPoint;
  96.         private Point endPoint;
  97.  
  98.         public void setStartPoint(Point startPoint) {
  99.             this.startPoint = startPoint;
  100.         }
  101.  
  102.         public void setEndPoint(Point endPoint) {
  103.             this.endPoint = endPoint;
  104.         }
  105.     }
  106.  
  107. }
  108.  
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
Main.java:7: error: class PaintLine is public, should be declared in a file named PaintLine.java
public class PaintLine extends JFrame {
       ^
1 error
stdout
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Standard output is empty
https://ideone.com/dbwyio
language:
Java (HotSpot 12)
created:
6 years ago
visibility:
secret

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