package hello;

import java.util.Scanner;//Scanner is in java.util 

public class  Hello

{ 

public static void main(String[] args)

{

System.out.println("please set in a string ");

//creat a Scanner

Scanner scanner=new Scanner(System.in);//new Scanner（System.in）是创建一个Scanner类型的对象，语法Scanner scanner 声明scanner是一个Scanner类型的变变量 

String name=scanner.next();

System.out.println(name);

}

}

//计算圆的面积从控制台输入数据

package hello;

import java.util.Scanner;

public class Hello

{

public static void main(String[] args)

{

double area;

//Creat a scanner

    Scanner scanner=new Scanner(System.in);

    //让用户输入数据

    System.out.println("请输入圆的半径");

    int r=scanner.nextInt();

    area=r*r*3.14;

    System.out.println("面积是："+area);//这里的加号是字符串连接符

}

}