用get和set取值来计算长方形的周长和面积（包括成员方法和构造方法）

public class Rectangle {private int length;private int width;public Rectangle(){}public void setA(int length,int width){this.length=length;this.width=width;}public int getA(){return this.length;}public int getA1(){return this.width;}public int area(){return length*width;}public int perimeter(){return 2*(length+width);}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubRectangle rectangle=new Rectangle();rectangle.setA(2,3);rectangle.getA();rectangle.getA1();rectangle.area();rectangle.perimeter();System.out.println("面积是"+rectangle.area());System.out.println("周长是"+rectangle.perimeter());}}