histogram.java

generating histogram

import javax.swing.*;

import java.awt.*;



public class Histogram extends JPanel {

  // Count the occurrence of 26 letters
  private int[] count;



  /** Set the count and display histogram */

  public void showHistogram(int[] count) {

    this.count = count;

    repaint();

  }



  /** Paint the histogram */

  protected void paintComponent(Graphics g) {

    if (count == null) return; // No display if count is null


    super.paintComponent(g);



    // Find the panel size and bar width and interval dynamically
    int width = getWidth();

    int height = getHeight();

    int interval = (width - 40) / count.length;

    int individualWidth = (int)(((width - 40) / 24) * 0.60);



    // Find the maximum count. The maximum count has the highest bar
    int maxCount = 0;

    for (int i = 0; i < count.length; i++) {

      if (maxCount < count[i])

        maxCount = count[i];

    }



    // x is the start position for the first bar in the histogram
    int x = 30;



    // Draw a horizontal base line
    g.drawLine(10, height - 45, width - 10, height - 45);

    for (int i = 0; i < count.length; i++) {

      // Find the bar height
      int barHeight =

        (int)(((double)count[i] / (double)maxCount) * (height - 55));



      // Display a bar (i.e. rectangle)
      g.drawRect(x, height - 45 - barHeight, individualWidth,

        barHeight);



      // Display a letter under the base line
      g.drawString((char)(65 + i) + "", x, height - 30);



      // Move x for displaying the next character
      x += interval;

    }

  }



  /** Override getPreferredSize */

  public Dimension getPreferredSize() {

    return new Dimension(300, 300);

  }

}