Java读一行写一行工具类

package cn.tedu.net;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
 
//这个类用来测试一行一行读取，一行一行写出
//读取一行数据 BufferedReader.readLine()
//一行一行写出 PrintWriter.println()
public class TestIO {
    public static void main(String[] args) {
       try {
           //1，创建BufferedReader对象
           BufferedReader in = new BufferedReader(new FileReader("D:\\iotest\\1.txt"));
           String line;//定义变量，记录每行读取到的数据
           //2，readLine()读取一行时，会读取特殊标记：换行符 \r \n
           //只要有数据就一直读取,没数据时，readLine()返回null
           while( ( line=in.readLine() ) != null) {
              System.out.println(line);
           }
           //3，释放资源
           in.close();
           //一行一行写出？PrintWriter.println()
           PrintWriter out = new PrintWriter(new FileWriter("D:\\iotest\\1.txt"));
           out.println("hello");
           out.println("java");
           out.close();
       } catch (IOException e) {
           e.printStackTrace();
       }
    }
}