wormlink.java

SUN官方的资料

/*
 * @(#)WormLink.java	1.6 02/07/25 @(#)
 *
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 * PROPRIETARY/CONFIDENTIAL
 * Use is subject to license terms.
 */

/*
 * WormLink.java
 *
 * Created on March 30, 2001, 16:15
 * @author Todd M Kennedy
 * @version 1.0
 */

package example.wormgame;

/**
 * WormLink represents one sub-section of a worm. Because the
 * worm will usually contain a few straight segments, this is
 * a relatively cost effective way to store the entire worm.
 * The [X,Y] coordinates are the "tail" of the worm. The link
 * is drawn starting at the tail and proceeding "len" spaces
 * in direction "dir".
 */
public class WormLink {

    private int x, y;
    private int len;
    private byte dir;

    private WormLink() {
    }

    public WormLink(int startX, int startY, int length, byte direction) {
	x = startX;
	y = startY;
	dir = direction;
	len = length-1;
    }

    /**
     * Create a worm link with a length of 1. This contstructor is
     * used when the worm changes direction.
     */
    public WormLink(int startX, int startY, byte direction) {
	this(startX, startY, 1, direction);
    }

    /**
     * Add one cell length to the head of this segment.
     */
    public void increaseLength() {
	len++;
    }

    /**
     * Remove one cell length from the tail of this segment.
     */
    public void decreaseLength() {
	len--;
	switch (dir) {
	case Worm.LEFT:
	    x--;
	    break;
	case Worm.RIGHT:
	    x++;
	    break;
	case Worm.UP:
	    y--;
	    break;
	case Worm.DOWN:
	    y++;
	    break;
	}
    }

    /**
     * Get the length, in cells, of this segment.
     */
    public int getLength() {
	return len+1;
    }

    /**
     * Get the X coordinate of the cell that contains the head of this
     * worm segment.
     */
    public int getX() {
	return x;
    }

    /**
     * Get the Y coordinate of the cell that contains the head of this
     * worm segment.
     */
    public int getY() {
	return y;
    }

    /**
     * Get the X coordinate of the cell that contains the tail of this
     * worm segment.
     */
    public int getEndX() {
	if (dir == Worm.LEFT) 
	    return x-len;
	if (dir == Worm.RIGHT)
	    return x+len;
	return x;
    }

    /**
     * Get the Y coordinate of the cell that contains the tail of this
     * worm segment.
     */
    public int getEndY() {
	if (dir == Worm.DOWN)
	    return y+len;
	if (dir == Worm.UP)  
	    return y-len;
	return y;
    }
    
    /**
     * Get the direction this worm segment is pointing.
     */
    public byte getDirection() {
	return dir;
    }

    /**
     * Returns true if the worm segment is at the given cell
     */
    public boolean contains(int x, int y) {
	switch (dir) {
	case Worm.LEFT:
	    return ((y == this.y) && ((x <= this.x) && (x >= getEndX())));
	case Worm.RIGHT:
	    return ((y == this.y) && ((x >= this.x) && (x <= getEndX())));
	case Worm.UP:
	    return ((x == this.x) && ((y <= this.y) && (y >= getEndY())));
	case Worm.DOWN:
	    return ((x == this.x) && ((y >= this.y) && (y <= getEndY())));
	}
	return false;
    }

    /**
     * Debug method.
     */
    public String toString() {
	String dirString;
	switch (dir) {
	case Worm.LEFT:
	    dirString = "Left";
	    break;
	case Worm.RIGHT:
	    dirString = "Right";
	    break;
	case Worm.UP:
	    dirString = "Up";
	    break;
	case Worm.DOWN:
	    dirString = "Down";
	    break;
	default:
	    dirString = "UNKNOWN -- " + dir;
	}
	
	return " pos == [" + x + "," + y + "]" +
	    " - [" + getEndX() + "," + getEndY() + "]" +
	    "   len == " + getLength() + 
	    "   dir == " + dirString;
    }
}