嗨，我正在解决这个问题，假设一个图书馆正在处理一个包含书名的输入文件，以便识别重复的图书。编写一个程序，从名为booktitles.inp的输入文件中读取所有标题，然后将它们写入名为duplicatetitles.out的输出文件。完成后，输出文件应包含输入文件中重复的所有标题。请注意，即使输入文件可能多次包含相同的标题，重复的标题也应写入一次。如果输入文件中没有重复的标题，则输出文件应为空。使用记事本或其他文本编辑器创建输入文件，每行一个标题。确保你有许多副本，包括一些有三个或更多副本。
到目前为止，我有这个，但它是打印重复不止一次，如果我改变输入文件的顺序。谢谢。

import java.io.*; 
      public class Library
      { 
      public static void main(String[] args) throws IOException
      { 
      String line3="";
      boolean dup = false;
      // PrintWriter object for output.txt 
      PrintWriter pw = new PrintWriter("C:\\Users\\Ilyas\\Desktop\\tempBookTitles.txt"); 
      PrintWriter pw2 = new PrintWriter("C:\\Users\\Ilyas\\Desktop\\duplicateTitles.txt");
      // BufferedReader object for input.txt 
      BufferedReader br1 = new BufferedReader(new 
      FileReader("C:\\Users\\Ilyas\\Desktop\\bookTitles.txt")); //read input file
      String line1 = br1.readLine(); 
      // loop for each line of input.txt 
      while(line1 != null) 
      {   
      boolean flag = false; 
      // BufferedReader object for output.txt 
      BufferedReader br2 = new BufferedReader(new 
      FileReader("C:\\Users\\Ilyas\\Desktop\\tempBookTitles.txt"));
      BufferedReader br3 = new BufferedReader(new 
      FileReader("C:\\Users\\Ilyas\\Desktop\\duplicateTitles.txt"));  //try 
      String line2 = br2.readLine(); 
        // loop for each line of output.txt 
        while(line2 != null) 
        { 
            if(line1.equals(line2)) 
            { 
                line3 = br3.readLine();
                flag = true;

                if(line1.equals(line3))
                {
                    line1 = null;
                }
                else
                {
                    pw2.println(line1);
                    pw2.flush();            
                    //break; 
                }
                }
            } 
            line2 = br2.readLine(); 
        } 
        // if flag = false 
        // write line of input.txt to output.txt 
        if(flag==false)
        {                                                
        pw.println(line1);                   //print to temp file, delete temp file at end
        pw.flush(); 
        } 
        line1 = br1.readLine(); 
        } 

        br1.close(); 
        pw.close(); 
        pw2.close();
        System.out.println("File operation performed successfully"); 
        } 
        }