Scanner

Posted 2020-12-31 yu-zhi

 1 package cn.itcast_01;
 2 /* 
 3 Scanner: 用于接收键盘录入数据.
 4 录入数据格式:
 5     导包,创建对象,调用方法
 6     
 7 System类下有一个静态字段:
 8     public static final InputStream in; 标准输入流, 对应键盘输入
 9     InputStream is = System.in;
10     
11 class Demo
12 {
13     public static final int x = 10;
14     public static final Student s = new Student();
15     
16 }
17 int y = Demo.x;
18 Student s = Demo.s;
19 
20 构造方法:
21     Scanner(InputStream source)
22 
23  */
24  
25 import java.util.Scanner;
26 public class ScannerDemo
27 {
28     public static void main(String[] args){
29         //创建对象 
30         Scanner s = new Scanner(System.in);
31         int x = s.nextInt();
32         System.out.println("x = " + x);
33     }
34 }

/* 
基本格式:
    public boolean hasNextXxx(): 判断是否为某事类型的元素
    public Xxx nextXxx(): 获取该元素
    
举例: int 类型
    public boolean hasNextInt()
    public int nextInt()
注意:
    InputMismatchException: 输入不匹配异常


 */

package cn.itcast_02;
import java.util.Scanner;
public class ScannerDemo2
{
    public static void main(String[] args){
        //创建对象
        Scanner sc = new Scanner(System.in);
        //输入字符串导致InputMisMatchException;
        // int x = sc.nextInt();
        // System.out.println("x = " + x);
        
        if(sc.hasNextInt()){
            int x = sc.nextInt();
            System.out.println("x = " + x);
        }else{
            System.out.println("你输入错误");
        }
    }
}