heapoffish.java

深入java 虚拟机中的一个Java程序

/*
 * Copyright (c) 2005 Your Corporation. All Rights Reserved.
 */
import java.awt.*;
import java.applet.*;

/**
* This applet simulates a compacting, mark-and-sweep
* garbage-collected heap inside a Java Virtual Machine.
*
* @author  Bill Venners
*/
/*
<applet code=HeapOfFish.class height=500 width=600>
</applet>
*/
public class HeapOfFish extends Applet {

    private GCHeap gcHeap = new GCHeap(15, 50);
    private LocalVariables localVars = new LocalVariables();

    private HeapOfFishControlPanel controlPanel = new HeapOfFishControlPanel();
    private HeapOfFishCanvases canvases = new HeapOfFishCanvases(gcHeap, localVars, controlPanel.getTextArea());
    private String currentHeapOfFishMode = HeapOfFishStrings.swim;

    public void init() {

        super.init();
        setBackground(Color.cyan);

        setLayout(new BorderLayout(5, 5));
        add("North", new ColoredLabel("HEAP OF FISH", Label.CENTER, Color.white));
        add("South", controlPanel);
        add("Center", canvases);
    }

    public void start() {
        canvases.start();
    }

    public void stop() {
        canvases.stop();
    }

    public Insets insets() {
        return new Insets(5, 5, 5, 5);
    }

    public boolean action(Event evt, Object arg) {
        if (evt.target instanceof Checkbox) {
            Checkbox cb = (Checkbox) evt.target;
            String cbname = cb.getLabel();
            if (cbname.equals(HeapOfFishStrings.allocateFish)) {
                if (!currentHeapOfFishMode.equals(HeapOfFishStrings.allocateFish)) {
                    controlPanel.getTextArea().setText(HeapOfFishStrings.allocateFishInstructions);
                    canvases.setMode(HeapOfFishStrings.allocateFish);
                }
            }
            else if (cbname.equals(HeapOfFishStrings.assignReferences)) {
                if (!currentHeapOfFishMode.equals(HeapOfFishStrings.assignReferences)) {
                    canvases.setMode(HeapOfFishStrings.assignReferences);
                }
            }
            else if (cbname.equals(HeapOfFishStrings.garbageCollect)) {
                if (!currentHeapOfFishMode.equals(HeapOfFishStrings.garbageCollect)) {
                    canvases.setMode(HeapOfFishStrings.garbageCollect);
                }
            }
            else if (cbname.equals(HeapOfFishStrings.compactHeap)) {
                if (!currentHeapOfFishMode.equals(HeapOfFishStrings.compactHeap)) {
                    controlPanel.getTextArea().setText(HeapOfFishStrings.compactHeapInstructions);
                    canvases.setMode(HeapOfFishStrings.compactHeap);
                }
            }
            else if (cbname.equals(HeapOfFishStrings.swim)) {
                if (!currentHeapOfFishMode.equals(HeapOfFishStrings.swim)) {
                    controlPanel.getTextArea().setText("");
                    canvases.setMode(HeapOfFishStrings.swim);
                }
            }
            currentHeapOfFishMode = cbname;
            canvases.repaint();
        }
        return true;
    }
}