以随机设置绘制一系列同心圆

我真的很困惑如何进行编程。需要使用Java的drawArc方法绘制一系列8个同心圆，条件如下

使用导入 java.util.Random 库

1. 提供在随机位置（即 x-y 坐标必须随机计算）。
2. 为每个圆圈提供随机颜色
3. 为每个圆提供随机直径

我当前的代码能够为每个圆圈获取随机颜色，但不清楚如何满足其他随机条件

// 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
}

进行此类练习的关键有几点：

• 从圈数和步长的常数开始；特别是随机数生成器只需要创建一次。

  private static final int N = 8;
  private static final int S = 32;
  private static Random random = new Random();
  

• 选择坐标落在绘图区域内的随机点。

  // a random point inset by S
  int x = random.nextInt(getWidth() - S * 2) + S;
  int y = random.nextInt(getHeight() - S * 2) + S;
  

• 对于每个圆，找到直径作为以下函数的函数S，添加一个步骤的随机分数，并在所选点处渲染按半径偏移的圆弧。

  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);
  }
  

• 调整封闭框架的大小，这会强制repaint()，看看效果。

• 由于随机颜色并不总是有吸引力，请考虑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));
  

• 覆盖getPreferredSize() https://stackoverflow.com/q/7229226/230513确定绘图面板尺寸。

  private static final int W = S * 12;
  private static final int H = W;
  …
  @Override
  public Dimension getPreferredSize() {
      return new Dimension(W, H);
  

• 也可以看看初始线程 http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html.