为什么这行char g =(char)(br.read()); 被跳过？

Question

在这个程序中,char g = (char)(br.read())每当我运行程序时都会跳过该行.进入年龄后,如果我输入性别为m,我收到错误java.lang.NumberFormatException.

import java.io.*;
public class Tax
{
    public static void main()throws IOException
    {
        InputStreamReader isr  = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        System.out.println("Enter age");
        int age = Integer.parseInt(br.readLine());
        System.out.println("Enter gender as m or f");
        char g = (char)(br.read());
        System.out.println("Enter Taxable Income");
        int ti = Integer.parseInt(br.readLine());
        double in;
        if (age > 65 || g == 'f')
        System.out.println("Wrong Category");
        else
        {
            if (ti <= 160000)
            in = 0;
            else if(ti > 160000 && ti<=500000)
            in = (ti - 160000) * (10.0/100.0);
            else if(ti > 500000 && ti<=800000)
            in = (ti - 50000) * (20.0/100.0) + 34000;
            else
            in = (ti - 800000) * (30.0/100.0) + 94000;
            System.out.println("Income Tax = " + in);
        }
    }
}

但是如果程序被修改如下,即如果char g = (char)(br.read());被替换String g = br.readLine(),则它可以工作

import java.io.*;
public class Tax
{
    public static void main()throws IOException
    {
        InputStreamReader isr  = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        System.out.println("Enter age");
        int age = Integer.parseInt(br.readLine());
        System.out.println("Enter gender as m or f");
        String g = br.readLine();
        System.out.println("Enter Taxable Income");
        int ti = Integer.parseInt(br.readLine());
        double in;
        if (age > 65 || g.equalsIgnoreCase("f"))
        System.out.println("Wrong Category");
        else
        {
            if (ti <= 160000)
            in = 0;
            else if(ti > 160000 && ti<=500000)
            in = (ti - 160000) * (10.0/100.0);
            else if(ti > 500000 && ti<=800000)
            in = (ti - 50000) * (20.0/100.0) + 34000;
            else
            in = (ti - 800000) * (30.0/100.0) + 94000;
            System.out.println("Income Tax = " + in);
        }
    }
}

Answer 1

问题是你只是从阅读器中读取一个字符 - 仍然要读取行分隔符部分.

所以如果BufferedReader逻辑上包含:

30\r\nm\r\n20

然后:

• readLine()第一次打电话会消耗掉"30\r\n".
• read()然后呼叫将消耗"m"离开\r\n20
• readLine()第二次调用将消耗"\r\n",返回一个空字符串

如果你实际输入 "30",点击返回,然后输入"m20"并点击返回,它会起作用 - 但显然这不是你想要的:)

要么使用扫描仪,要么只使用readLine()并检查"m"和"f"的行内容.