wormlink.java

j2me编的吞吃蛇

/*
 * @(#)WormLink.java	1.3 03/08/10
 *
 * Copyright (c) 2000-2003 Sun Microsystems, Inc. All rights reserved.
 * PROPRIETARY/CONFIDENTIAL
 * Use is subject to license terms
 */

/*
 * WormLink.java
 *
 * Created on March 30, 2001, 16:15
 * @version 1.3
 */

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;
    }
}