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);
  }
}