递归子程序法：对应每个非终结符语法单元编一个独立的处理过程（或子程序）。语法分析从读入第一个单词开始

					package point;							// 定义Java包，包名为point
					/** 
					 * Java语言实验参考程序
					 * Company 北京师范大学计算机系				 
					 * @author 孙一林
					 * @version 1.0
					 */
					class Point {						// 声明一个“点”类
					  private int x0;
					  private int y0;
					  private int x;
					  private int y;
					  public Point() {
					    this.x0 = 0;
					    this.y0 = 0;
					    this.x = 0;
					    this.y = 0;
					  }
					  public Point(int newX0,int newY0) {
					    this.x0 = newX0;
					    this.y0 = newY0;
					    this.x = newX0;
					    this.y = newX0;
					  }
					  public void setX(int newX) {
					    x = newX + x0;
					  }
					  public int getX() {
					    return x;
					  }
					  public void setY(int newY) {
					    y = newY + y0;
					  }
					  public int getY() {
					    return y;
					  }
					}