scanner

package 基础;

import java.util.Scanner;

public class demo01 {
    int  a =0;
    float f=0.0f;
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入整数");
        if(scanner.hasNextInt()){
            String i=scanner.nextLine();
            System.out.println(i);
        }else {
            System.out.println("输入的不是整数数据");}
            System.out.println("请输入小数");
            if (scanner.hasNextFloat()) {
                String f = scanner.nextLine();
                System.out.println(f);

            }else{
                System.out.println("输入的不是小数数据");}

        scanner.close();


    }
}

求和以及平均数：
public class Sum {


    public static void main(String[] args) {
        double sum = 0;
        int s = 0;
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextDouble()) {
            double x = scanner.nextDouble();
            s = s + 1;
            sum = sum + x;
            System.out.println("输入第" + s + "次");
        }
        System.out.println("总和为" + sum);
        System.out.println("平均数为" + sum / s);
        scanner.close();
        ;
    }
}