求代码（1）java设计一个长方形类,合理设置其应有的属性,分别输出长方形的周长和面积.

public class rectangle
{
double a;
double b;
double perimeter;
double area;
public rectangle(double a,double b)//长方形
{
this.a=a;
this.b=b;
this.perimeter=(a+b)*2;
this.area=a*b;
}
public rectangle(double a)//正方形
{
this.a=a;
this.perimeter=4*a;
this.area=a*a;
}
public double getPerimeter()
{
return perimeter;
}
public double getArea()
{
return area;
}
}
下面是测试：
public class test1 {
public static void main(String args[])
{
rectangle rt1=new rectangle(3,4);
System.out.println("长方形的周长是"+rt1.getPerimeter());
System.out.println("长方形的面积是"+rt1.getArea());
rectangle rt2=new rectangle(3);
System.out.println("正方形的周长是"+rt2.getPerimeter());
System.out.println("正方形的面积是"+rt2.getArea());
}
}