以下代码是在学习读取文件与写入文件一起写的，读取文件时 String 换成 Stringbuffer 提高代码运行速度，ready() 方法判断文件是否准备好被读取，如果为 null，则停止。同时可以确保 Stringbuffer 不会报空指针异常。

import java.io.*;

public class FileGet {
    public static void main(String[] args) {
        try {
            BufferedWriter out = new BufferedWriter(new FileWriter("runoob.txt"));
            out.write("菜鸟教程");
            out.append("dasd");
            out.newLine();
            out.write("你好");
            out.flush();
            out.close();
            System.out.println("文件创建成功！");
            BufferedReader in = new BufferedReader(new FileReader("runoob.txt"));
            StringBuffer sb;
            while (in.ready()) {
                sb = (new StringBuffer(in.readLine()));
                System.out.println(sb);
            }
            in.close();
        } catch (IOException e) {
        }
    }
}