Scanner

Scanner

package com.kuang.scanner;

import java.util.Scanner;

public class Demo01 {
    public static void main(String[] args) {
        //创建一个扫描器对象，用于接收键盘数据
        Scanner scanner = new Scanner(System.in);

        System.out.println(scanner);
        //判断用户有没有输入字符串
        if(scanner.hasNext()){
            //使用next方式接收
            String str = scanner.next();//程序会等待用户输入
            System.out.println("输出的内容为:"+str);
        }

        //凡是属于IO流的类如果不关闭会一直占用资源，要养成好习惯用完就关掉
        scanner.close();
    }
}

package com.kuang.scanner;

import java.util.Scanner;

public class Demo02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println(scanner);

        if (scanner.hasNextLine()){//能输出空格
            String str = scanner.nextLine();
            System.out.println("输出的内容为:"+str);
        }
        scanner.close();
    }


}

package com.kuang.scanner;

import java.util.Scanner;

public class Demo03 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
       String str = scanner.nextLine();
        System.out.println("输出的内容为:"+str);
        scanner.close();

    }

}

package com.kuang.scanner;

import java.util.Scanner;

public class Demo04 {
    public static void main(String[] args) {
        int i =0;
        float f = 0.0f;
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入整数：");
        if(scanner.hasNextInt()){
            i = scanner.nextInt();
            System.out.println("整数数据:"+i);
        }else {
            System.out.println("输入的不是整数");
        }

        System.out.println("请输入小数：");
        if(scanner.hasNextFloat()){
            f = scanner.nextFloat();
            System.out.println("小数数据:"+f);
        }else {
            System.out.println("输入的不是小数");
        }
        scanner.close();
    }
}

package com.kuang.scanner;

import java.util.Scanner;

public class Demo05 {
    //我们可以输入多个数字，并求其总和与平均数，每输入一个数字用回车确认，通过输入非数字来结束输入并输出执行结果
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //和
        double sum = 0.0;
        //输入了多少个数字
        int m = 0;
        while(scanner.hasNextDouble()){
            double x = scanner.nextDouble();
            sum+=x;
            m++;
        }
        System.out.println(m+"个数字和为:"+sum);
        System.out.println(m+"个数字平均数为:"+sum/m);


        scanner.close();
    }
}