从控制台读取输入

一、标准的输入/输出

　　System.out 表示标准的输出设备：使用println方法显示基本值或字符串。

　　System.in 表示标准的输入设备：Java不直接支持控制台输入。

二、创建Scanner类的对象、以来读取来自System.in的输入

 三、Scanner对象的方法

　　

方法	描述

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

四、实例

1.next()

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Scanner input = new Scanner(System.in); System.out.print("Enter three words separated by spaces:"); String s1 = input.next(); String s2 = input.next(); String s3 = input.next(); System.out.println("sl is " + s1); System.out.println("s2 is " + s2); System.out.println("s3 is " + s3);

 

 

 

 

 

 

 

 

 

2.nextLine()

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Scanner input = new Scanner(System.in); System.out.print("Enter a line:"); String s = input.nextLine(); System.out.println("The line entered is " + s)

 

 

 

 

 

 

3.计算平均值

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import java.util.Scanner; public class ComputeAverage{   public static void main(String[] args) {     Scanner input = new Scanner(System.in);     System.out.print("Enter three numbers:");     double number1 = input.nextDouble();     double number2 = input.nextDouble();     double number3 = input.nextDouble();        double average = (number1 + number2 + number3) / 3;     System.out.println("The average of " + number1 + " " +              number2 + " " + number3 + " is " + average);    } }

 

 

 

 

 

 

 

 

 

 

 

 

运行结果：

 

 

4. 计算圆面积

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import java.util.Scanner; public class ComputeArea{   public static void main(String[] args) {     Scanner input = new Scanner(System.in);     System.out.print("Enter a number for radius: ");     double radius = input.nextDouble();     double area = radius * radius * 3.14159;     System.out.println("The area for the circle of radius " +   radius + " is " + area);     } }

 

 

 

 

 

 

 

 

 

 

 

 

运行结果：