Scanner

package 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);//程序会等待用户输入完毕
        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("输入的内容为:"+str);
        }
        //凡是属于IO流的类如果不关闭会一直占用资源,要养成良好习惯用完就关掉
        scanner.close();

    }
}

package scanner;

import java.util.Scanner;

public class Dmeo02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("使用nextline方式接收:");
        if (scanner.hasNext()){
            String src = scanner.nextLine();
            System.out.println("输出的内容为:"+src);
        }
        scanner.close();
    }
}

package scanner;

import java.util.Scanner;

public class Dmeo03 {
    public static void main(String[] args) {
        //从键盘接收数据
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入数据:");

        String src = scanner.nextLine();

        System.out.println("输出的内容为:"+src);

        scanner.close();
    }
}

package scanner;

import java.util.Scanner;

public class Dmeo04 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //从键盘接收数据
        int i = 1;
        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:");
        }
        System.out.println("请输入小数:");
        //如果...那么
        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!");
        }
    }
}

package scanner;

import java.util.Scanner;

public class Demo05 {
    public static void main(String[] args) {
        //我们可以输入多个数字,并求起总和与平均数,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;
        Scanner scanner = new Scanner(System.in);
        //和
        double sum = 0;
        //计算输入了多少个数字
        int m = 0;
        System.out.println("请输入数字:");
        //通过循环判断是否还有输入,并在里面对每一次进行求和和统计
        while (scanner.hasNextDouble()){
            double x = scanner.nextDouble();
            m = m + 1;///m++
            sum = sum+x;
            System.out.println("你输入了第"+m+"个数据,然后当前结果sum="+sum);
        }
        System.out.println(m + "个数的和为" + sum);
        System.out.println(m + "个数的平均值为" + (sum/m));
        scanner.close();
    }
}

hasNextInt() 判断是否有整数输入

NextInt() 要求从键盘输入