Scanner的使用

package Sanner;

import java.util.Scanner;

public class Demo01 {
    public static void main(String[] args) {
        //创建一个扫描器对象，用于接受键盘数据
        new Scanner(System.in);//out输出  in输入
        Scanner scanner = new Scanner(System.in);
        System.out.println("使用next方式接收");

        //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();
            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，要习惯用完就关
        scanner.close();
    }
}
==================================================================================

package Sanner;

import java.util.Scanner;

public class Demo02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //从键盘接收数据
        System.out.println("使用nextLine方式接收");

        if(scanner.hasNextLine());{
            //判断是否还有输入
        String str = scanner.nextLine();
        //等待用户输入
        System.out.println("输出的内容为："+str);
    }
    scanner.close();
    }
}

==================================================================================

package Sanner;

import java.util.Scanner;

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

==================================================================================

package Sanner;

import java.util.Scanner;

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

        scanner.close();
    }
}

==================================================================================

package Sanner;

import java.util.Scanner;

public class Demo05 {
    public static void main(String[] args) {
        //题:需要可以输入多个数字，并求其总和于平均数，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
        Scanner scanner = new Scanner(System.in);

        //和
        double sum = 0;
        //计算输入了多少个数字
        int m = 0;
        //
        //通过循环判断是否还有输入，并在里面对每一次进行求和与统计
        while (scanner.hasNextDouble()) {
            double x = scanner.nextDouble();
            m = m++;
            sum = sum + x;
        }
        System.out.println(m+"个数的和为"+sum);
        System.out.println(m+"个数的平均值是"+(sum/m));
        scanner.close();
    }
}

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