浅析Java Scanner 类的用法

import java.util.Scanner; 
 
public class ScannerDemo {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    // 从键盘接收数据
 
    // next方式接收字符串
    System.out.println("next方式接收：");
    // 判断是否还有输入
    if (scan.hasNext()) {
      String str1 = scan.next();
      System.out.println("输入的数据为：" + str1);
    }
    scan.close();
  }
}

import java.util.Scanner;
 
public class ScannerDemo {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    // 从键盘接收数据
 
    // nextLine方式接收字符串
    System.out.println("nextLine方式接收：");
    // 判断是否还有输入
    if (scan.hasNextLine()) {
      String str2 = scan.nextLine();
      System.out.println("输入的数据为：" + str2);
    }
    scan.close();
  }
}

import java.util.Scanner;
 
public class ScannerDemo {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    // 从键盘接收数据
    int i = 0;
    float f = 0.0f;
    System.out.print("输入整数：");
    if (scan.hasNextInt()) {
      // 判断输入的是否是整数
      i = scan.nextInt();
      // 接收整数
      System.out.println("整数数据：" + i);
    } else {
      // 输入错误的信息
      System.out.println("输入的不是整数！");
    }
    System.out.print("输入小数：");
    if (scan.hasNextFloat()) {
      // 判断输入的是否是小数
      f = scan.nextFloat();
      // 接收小数
      System.out.println("小数数据：" + f);
    } else {
      // 输入错误的信息
      System.out.println("输入的不是小数！");
    }
    scan.close();
  }
}

import java.util.Scanner;
 
class ScannerDemo {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
 
    double sum = 0;
    int m = 0;
 
    while (scan.hasNextDouble()) {
      double x = scan.nextDouble();
      m = m + 1;
      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));
    scan.close();
  }
}