java简单练习

1.

import java.util.Scanner;
public class Area {
public static void main(String[] args)
{

//求圆的面积
Scanner input=new Scanner(System.in);
double r=input.nextDouble();
double a=r*r*3.14;
System.out.println(a);
}


}

2.import java.util.Scanner;
public class area2 {

//求圆的面积
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
        double r=input.nextDouble();
        double a=r*r*3.1415926;
        System.out.println(a);
}


}

3.

import java.util.Scanner;
//求三个数的平均数
public class Aveg {


public static void main(String[] args) {
// TODO Auto-generated method stub
     Scanner input = new Scanner(System.in);
     double a = input.nextDouble();
     double b = input.nextDouble();
     double c = input.nextDouble();
     System.out.println((a+b+c)/3);
}


}

4.import javax.swing.JOptionPane;
public class Message {
public static void main(String[] args)
{

//对话框显示内容
JOptionPane.showMessageDialog(null," Welcom java!");
}


}