adaptivehuff.java

用java实现的自适应哈夫曼算法

import java.awt.*;
import java.util.*;
import InputField;
import OutputField;
import Send;
import BitStats;



public class AdaptiveHuff extends AdaptiveTree
{

public void init()
{
    super.init();

    setLayout(null);
    size = size();

    super.setFont(defaultFont);


	inputField = new InputField();
	add(inputField);
	inputField.reshape(5, 7, (size.width/3), (_height + _descent) );

	outputField = new OutputField();
	add(outputField);
	outputField.reshape( (size.width*2/3), 7, (size.width/3), (_height + _descent) );

	sender = new Send();
	add(sender);
	sender.reshape( 5, (size.height*2/3 + _height+_descent), (size.width - 10), (_height + _descent) );


    dispRect = new Rectangle(5, (3*_ascent),
			   size.width - 10,
			   size.height*2/3);

	message = new List();
	message.setMultipleSelections(false);
	add(message);
	message.reshape( 5, (size.height*2/3 + 2*(_height+_descent)), (size.width/2), (size.height/3 - 2*(_height+_descent)) );
	addMessage("Adaptive tree initialized");

    this.setBackground(Color.white);
    waitforclick = true;

    mode = new CheckboxGroup();
    playpause = new Checkbox("Play-Pause", mode, waitforclick);
    continuous = new Checkbox("Continuous", mode, !waitforclick);
    add(playpause);
    add(continuous);
    playpause.reshape( (size.width/2)+10, (size.height*2/3 + 2*(_height+_descent)), (size.width/5), (_height+_descent) );
    continuous.reshape( (size.width/2)+10, (size.height*2/3 + 3*(_height+_descent)), (size.width/5), (_height+_descent) );

    next = new Button("Next Step");
    next.hide();
    add(next);
    next.reshape( (size.width/2)+10, (size.height*2/3 + 4*(_height+_descent)), (size.width/5), (_height+_descent) );

    stats = new BitStats(Color.white, Color.black);
    add(stats);
    stats.reshape( (size.width/2 + size.width/5 + 15), (size.height*2/3 + 2*(_height+_descent)), (3*size.width/10)-20, 4*(_height+_descent) );

	AdaptiveTree(51, dispRect);


}

public void updateTree(char newchar)
{
    int current;
    int max;


    try {                                           // first appearance for symbol
        current = findChar(newchar);                // Go to symbol external node
        max = highestInBlock(tree[current].count);  // Node number max in block?
        if (current != max && tree[current].parent != max) {
            addMessage("    Swapping nodes " +current+ " and " +max);
            swap(current, max);                     // Switch node with highest node in block
            pause();
            current = max;
        }
        addMessage("    Increasing count for '" +newchar+ "'");
        tree[current].count++;                      // Increment node weight
        pause();


    } catch (NoSuchElementException e) {            // Yes
        addMessage("    Spawning new node for '" +newchar+ "'");
        current = spawn(newchar);                   // NYT gives birth to new NYT and external node
        current = tree[current].parent;             // Go to old NYT node
        tree[current].count++;                      // Increment count of old NYT node
        pause();

   }

    while (current != root)                         // Is this the root node?
    {
        current = tree[current].parent;             // Go to parent node
        max = highestInBlock(tree[current].count);  // Node number max in block?
        if (current != max && tree[current].parent != max) {
            addMessage("    Swapping nodes " +current+ " and " +max);
            swap(current, max);             // Switch node with highest node in block
            pause();
            current = max;
        }

        tree[current].count++;                      // Increment node weight

    }

   	drawTrie(dispRect, null);

}

public void addMessage(String line)
{
    message.addItem(line);
    message.makeVisible(message.countItems() - 1 );
}




public void run()
{
    String code;
    char hold;
    int bitsent;

    try {

        hold = inputField.whatKey(_key);

    try {

        code = char2code( hold );
        addMessage("Character '" +hold+ "' FOUND:");
        addMessage("    Sending code for '" +hold+ "'");
        bitsent = char2code(hold).length();

    } catch (NoSuchElementException d) {

        addMessage("Character '" + hold + "' not found:");
        code = char2code(NYT) + (char)_key;
        addMessage ("   Sending NYT and character '" + hold + "'");
        pause();
        bitsent = char2code(NYT).length() + 8;

    }

    sender.wire(code);
    stats.addBits(8, bitsent);


    outputField.addString("" + hold );

    addMessage("Updating the tree:");
    updateTree(hold);

    } catch (NotValidChar d) {
    }

    update(gc);
    running = false;


}

    /*
     * Pause
     *
     * waits a few seconds. May also wait for a button press.
     */

    public synchronized void pause()
    {

        if (waitforclick) {
            try {
                next.show();
                update(gc);
                wait();
                next.hide();
            } catch (InterruptedException e) {};
        } else {
            try {
                wait(1000);
            } catch (InterruptedException e) {};
        }

        drawTrie(dispRect, null);
        update(gc);


    }



public synchronized boolean handleEvent(Event event) {

    if (event.target == next && event.id == Event.ACTION_EVENT) {
        notify();
    }

    if (event.target == continuous && event.id == Event.ACTION_EVENT) {
        waitforclick = false;
    }

    if (event.target == playpause && event.id == Event.ACTION_EVENT) {
        waitforclick = true;
    }

	return super.handleEvent(event);
}


public boolean keyDown(Event e, int key) {

        _event = e;
        _key = key;

        if (!running) {
            running = true;
            t = new Thread(this);
            t.start();
        }


    return true;
}

    boolean running;
    Event _event;
    int _key;

    Rectangle dispRect;                     // The area where the tree is displayed

   	InputField inputField;
   	OutputField outputField;
   	Send sender;
   	List message;

   	CheckboxGroup mode;
   	Checkbox playpause;
   	Checkbox continuous;
   	Button next;
   	BitStats stats;

    Dimension size;                         // The size of the applet

    Thread t;

}