这个代码怎么改就正确了？

Question

随机文件读写出:RandomAccessFile类import java.io.*;
public class ReadFileRW
{
public static void main(String []args)
{
StringBuffer sb=new StringBuffer();
char ch;
try
{
while((ch=(char)System.in.read())!="\n")
{
sb.append(ch);
}
RandomAccessFile raf=new RandomAccessFile("D:\\HelloWorld\\User.txt","rw");
raf.seek(raf.length());
raf.writeBytes(sb.toString());
raf.close();
}catch(Exception e)
{
e.printStackTrace();
}
}
}

Answer 1

while ((ch = (char) System.in.read()) != '\n')

Answer 2

import java.io.*;
public class ReadFileRW
{
    public static void main(String []args)
    {
        StringBuffer sb=new StringBuffer();
        char ch;
        try
        {
            while((ch=(char)System.in.read())!='\n')
            {
                sb.append(ch);
            }
            RandomAccessFile raf=new RandomAccessFile("D:\\HelloWorld\\User.txt","rw");
            raf.seek(raf.length());
            raf.writeBytes(sb.toString());
            raf.close();
        }catch(Exception e)
        {
            e.printStackTrace();
        }
    }
}

Answer 3

import java.io.*;
public class ReadFileRW
{
    public static void main(String []args)
    {
        StringBuffer sb=new StringBuffer();
        char ch;
        try
        {
            while((ch=(char)System.in.read())!='\n')
            {
                sb.append(ch);
            }
            RandomAccessFile raf=new RandomAccessFile("D:\\HelloWorld\\User.txt","rw");
            raf.seek(raf.length());
            raf.writeBytes(sb.toString());
            raf.close();
        }catch(Exception e)
        {
            e.printStackTrace();
        }
    }
}