import java.io.*;
public class zmcj{
public static void main(String args[])throws IOException{

BufferedReader buf=new BufferedReader(new InputStreamReader(System.in));
System.out.print("请输入一个字母: ");
String in=buf.readLine();
int n1=Integer.parseInt(in);
System.out.print(n1);

System.out.print("请输入另一个字母: ");
BufferedReader buf1=new BufferedReader(new InputStreamReader(System.in));
String in1=buf1.readLine();
int n2=Integer.parseInt(in1);
System.out.print(n2);

int out=n1-n2;
System.out.println(out);
}
}
这段程序怎么错呢？为什么输不出结果

字符串怎么转化成其他的类型呢？例如整型！

但是上面的输不出结果啊？

Exception in thread "main" java.lang.NumberFormatException: For input string: "W"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:447)
at java.lang.Integer.parseInt(Integer.java:497)
at String1.main(String1.java:5)

Process completed.

这个是抛出的异常