期末复习

void area()方法与 double area()方法、传入参数方法的区别

package demo1package;

public class Cylinder {
	double r;
	double pi;
	
	/*public class Cylinder {
	double r;
	double pi=3.14;
	
	double area(){
		return pi*r*r;
		
	}
	void area1(){
		System.out.println("面积是"+pi*r*r);
	}
	
}*/
	/////////////////////////////////////////////
	void number(double R,double PI){
		r=R;
		pi=PI;
		
	}
	double area(){
		return pi*r*r;
	}
}

　　

package demo1package;

public class text1 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Cylinder cylinder=new Cylinder();
		Cylinder cylinder2=new Cylinder();
		Cylinder cylinder3=new Cylinder();
		
		
		cylinder.pi=3.14;
		cylinder.r=5;
		
		cylinder2.pi=3.14;
		cylinder2.r=3;
		
		cylinder3.number(3,3.14);
		
		System.out.println("圆的半径是"+cylinder.r);
		System.out.println("圆的面积是"+cylinder.area());//double area();方法调用
		cylinder.area();//void area();方法调用
		
		System.out.println("圆2的半径是"+cylinder2.r);
		System.out.println("圆2的面积是"+cylinder.area());
		
		System.out.println("圆3的面积是"+cylinder.area());//三个参数方法
		
	}

}