java中怎么输入一个字符

import java.io.*; public class Test { public static void main(String[] args) throws IOException { BufferedReader buf = new BufferedReader (new InputStreamReader(System.in)); BufferedWriter buff = new BufferedWriter(new FileWriter("abc.txt")); String str = buf.readLine(); while(!str.equals("exit")) { buff.write(str); buff.newLine(); str = buf.readLine(); } buf.close(); buff.close(); } }