定义一个圆柱体类cylinder，并创建相应的对象，然后计算圆柱体的底面积与体积

 输入

2.8
5

package com;
import java.util.*;
class cylinder
{
    double radius;
    int height;
    double pi=3.14;
    void area() {
        System.out.println("底面积=" + pi * radius * radius);
    }
    double volume()
    {
        return (pi*radius*radius)*height;
    }
}
public class sentence {
    public static void main(String[] args) {
        cylinder volu;
        volu=new cylinder();
        Scanner reader=new Scanner(System.in);
        System.out.println("请输入圆柱的半径：");
        volu.radius= reader.nextDouble();
        System.out.println("请输入圆柱的高：");
        volu.height=reader.nextInt();
        System.out.println("低圆半径="+volu.radius);
        System.out.println("圆柱的高="+volu.height);
        System.out.print("圆柱");
        volu.area();
        System.out.println("圆柱体体积="+volu.volume());
    }
}

以圆柱类cylinder为例在类内部调用自己的方法

import java.util.*;
class cylinder
{
    double radius;
    int height;
    double pi=3.14;
    double area() {
       return pi * radius * radius;
    }
    double volume()
    {
        return area() * height;
    }
}
public class sentence {
    public static void main(String[] args) {
        cylinder volu;
        volu=new cylinder();
        Scanner reader=new Scanner(System.in);
        System.out.println("请输入圆柱的半径：");
        volu.radius= reader.nextDouble();
        System.out.println("请输入圆柱的高：");
        volu.height=reader.nextInt();
        System.out.println("低圆半径="+volu.radius);
        System.out.println("圆柱的高="+volu.height);
        System.out.print("圆柱");
        System.out.println("底面积=" +volu.area());
        System.out.println("圆柱体体积="+volu.volume());
    }
}

进一步，如果要强调是对象本身的成员话，则可以在成员名前加this关键字。即this.成员名

this代表调用此成员的对象

    double volume()
    {
        return this.area() * height;
    }

在圆柱体类cylinder中用变量调用方法

 

class cylinder
{
    double radius;
    int height;
    double pi=3.14;
    void setcylinder(double r,int h,double p)
    {
        pi=p;
        radius=r;
        height=h;
    }
    double area() {
       return pi * radius * radius;
    }
    double volume()
    {
        return this.area() * height;
    }
}
public class sentence {
    public static void main(String[] args) {
        double r;int h;
        cylinder volu;
        volu=new cylinder();
        Scanner reader=new Scanner(System.in);
        System.out.println("请输入圆柱的半径：");
        r=reader.nextDouble();
        System.out.println("请输入圆柱的高：");
        h=reader.nextInt();
        volu.setcylinder( r, h,3.14);
        System.out.println("低圆半径="+volu.radius);
        System.out.println("圆柱的高="+volu.height);
        System.out.print("圆柱");
        System.out.println("底面积=" +volu.area());
        System.out.println("圆柱体体积="+volu.volume());
    }
}