2021-4-15 计科1-3

package calc;
public class Test {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Square sq1,sq2;
        sq1 = new Square();
        sq2 = new Square(3.2);
        sq1.area();
        System.out.println("Sq2的周长是 "+ sq2.perimeter());
    }
}

package calc;
public class Square {
    double length;
    Square(){
        this.length = 2.0;
    }
    Square(double length){
        this.length = length;
    }
    public void area(){
        System.out.println("the area is "+ length * length);
    }
    public double perimeter(){
        return length * 6;
    }
}