java - 使用 int 作为 GregorianCalendar 的输入，但无法继续扫描 JAVA

Question

我试图编写一个代码来输入出生日期以返回当天的星期几，我使用输入流阅读器来获取我的输入

package testing;

import java.io.*;
import java.text.DateFormat;
import java.util.*;

public class theDayYouBorn {
    public static void main(String[] args) throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);

        System.out.println("Please Input the Year You Born at : ");
        int year1 = br.read();
        System.out.println("Thank!, Please input the Month :");
        int month1 = br.read();
        System.out.println("Okay, last thing Please input the day : ");
        int day1 = br.read();

        GregorianCalendar gc = new GregorianCalendar(year1, month1, day1);
        Date d1 = gc.getTime();
        DateFormat df = DateFormat.getDateInstance();
        String sd = df.format(d1);
        String dayName = gc.getDisplayName(gc.DAY_OF_WEEK, gc.LONG,
                Locale.getDefault());
        System.out.println("The Day you born in was a " + sd
                + " and the day was " + dayName);

    }
}

它让我只需输入第一个输入，然后运行它并生成一个随机日期，而不询问日期或月份

然后我尝试使用字符串作为输入并将它们转换为整数，它的工作......我改变了这一点:

System.out.println("Please Input the Year You Born at : ");
String year = br.readLine();
System.out.println("Thank!, Please input the Month :");
String preMonth = br.readLine();
System.out.println("Okay, last thing Please input the day : ");
String day = br.readLine();

int day1 = Integer.parseInt(day);
int month2 = Integer.parseInt(preMonth);
int year1 = Integer.parseInt(year);
int month1 = month2 - 1;

我试图理解为什么我无法扫描整数。

Answer 1

如果你看一下 documentation of read() method你会发现:

Reads a single character.

Returns:
The character read, as an integer in the range 0 to 65535 (0x00-0xffff), or -1 if the end of the stream has been reached

因此每次调用read都会返回一个char(或者更准确地说，它在Unicode表中的数字表示形式如'a'是97，或'1'是49)。

例如，如果下面的代码

System.out.println("Please Input the Year You Born at : ");
System.out.println(br.read());
System.out.println(br.read());
System.out.println(br.read());
System.out.println(br.read());
System.out.println(br.read());
System.out.println(br.read());

我们将提供输入1987

Please Input the Year You Born at : 
1987[here we press enter]

在 Windows 操作系统上，我们最终会得到

49
57
56
55
13
10

代表

int -> char
----------- 
49  -> '1'
57  -> '9'
56  -> '8'
55  -> '7'
13  -> '\r'
10  -> '\n'

在br.readLine();的情况下不存在这样的问题，因为它的目的是将数据作为文本而不是二进制数据读取。