FileReader in=new FileReader(".\\src\\Sample_7_4\\Hello.java");    //建立文件输入流

FileWriter out=new FileWriter("Hello.txt",true);

FileWriter out=new FileWriter("./Hello.txt",true);  //建立文件输出流

package Sample_7_4;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class IO2 {
  public static void main(String[] args) throws IOException{
    FileReader in=new FileReader(".\\src\\Sample_7_4\\Hello.java");    //建立文件输入流
    BufferedReader bin=new BufferedReader(in);    //建立缓冲输入流
    FileWriter out=new FileWriter("Hello.txt",true);  //建立文件输出流
    
    String str;
    while ((str=bin.readLine())!=null){
      System.out.println(str);
      out.write(str+"\n");
    }
    in.close();
    out.close();

  }
}