留下两个例子作为参考,

1. 追逐小方块的例子

2. HashMap 和 Iterator 的例子

 

Example one:

import acm.graphics.*;import acm.program.*;import java.awt.*;import java.awt.event.*;public class TargetSeeker extends GraphicsProgram {/* private constants */    private static final int TARGET_SIZE = 10;    private static final int SEEKER_SIZE = 20;    private static final int PAUSE_TIME = 10;        public void run() {        initTarget();        initSeeker();        addMouseListeners();                while (true) {            seek();        }    }        private void initTarget() {        targetSquare = new GRect(TARGET_SIZE, TARGET_SIZE);        targetSquare.setColor(Color.red);        targetSquare.setFilled(true);        targetX = getWidth() / 2;        targetY = getHeight() / 2;        add(targetSquare, targetX - TARGET_SIZE/2, targetY - TARGET_SIZE/2);    }        private void initSeeker() {        seeker = new GRect(SEEKER_SIZE, SEEKER_SIZE);        add(seeker, 0, 0);    }    private int moveAmount(double seekerPos, double targetPos) {        int amount = 0;        if (targetPos > seekerPos) {            amount = 1;        } else if (targetPos < seekerPos) {            amount = -1;        }        return amount;    }        private void seek() {        pause(PAUSE_TIME);        double seekerMidX = seeker.getX() + SEEKER_SIZE / 2;        int dx = moveAmount(seekerMidX, targetX);        double seekerMidY = seeker.getY() + SEEKER_SIZE / 2;        int dy = moveAmount(seekerMidY, targetY);                seeker.move(dx, dy);    }        public void mouseClicked(MouseEvent e) {        targetX = e.getX();        targetY = e.getY();        remove(targetSquare);        add(targetSquare, targetX - TARGET_SIZE/2, targetY - TARGET_SIZE/2);    }    /* private instance variable */    private int targetX;    private int targetY;    private GRect targetSquare;    private GRect seeker;}

 

Example two:

public void PrintMatchingKeys(HashMap
    
      map) {        ArrayList
     
       keys = new ArrayList
      
       ();        Iterator
       
         it = map.keySet().iterator();        while (it.hasNext()) {            // keys is array list, it is the key (String type) of map            keys.add(it.next());        }        // Reset "it" iterator to allow us to iterate over keys again        it = map.keySet().iterator();        while (it.hasNext()) {            String key = it.next();            String value = map.get(key);            // of course contain            if (key.contains(value)) {                println(key + ": " + value);            }        }    }