Question

JAVA PROGRAMMING LANGUAGE
Suppose a library is processing an input file containing the titles of books in order to identify duplicates. Write a program that reads all of the titles from an input file called bookTitles.inp and writes them to an output file called duplicateTitles.out. When complete, the output file should contain all titles that are duplicated in the input file. Note that the duplicate titles should be written once, even though the input file may contain same titles multiple times. If there are not duplicate titles in the input file, the output file should be empty. Create the input file using Notepad or another text editor, with one title per line. Make sure you have a number of duplicates, including some with three or more copies.

PLEASE WRITE A PROGRAM WITHOUT ANY ACCESS ERROR OR EXPLAIN HOW TO AVOID IT

Answer 1

I have implemented a java program which fetch book titles from the bookTitles.txt file then it will be stored into the HashSet and store the duplicate value using the arrayList and then store all the duplicate values to the duplicateTitles.txt file.

Here, I used HashSet which is used to store only single copy value. I does not store duplicate values.

How to fetch duplicate values using HashSet and ArrayList.

STEP 1: We store the values by checking it is not in the HashSet using the hashSet.contains() method which returns true if value is already into the hash set.

STEP 2: Then after which values that are already inserted into the hash set that are never stored into the hash set so that values we will store to the array list and we will get the duplicate Book Titles from the "bookTitles.txt" file.

Program:-

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;

public class GenerateDuplicateBookTitle {
    
    public static void main(String[] args) {
        
        // declare and intialize path whereyour input file is stored
        String filePath = "D:\\";
        
        // intialize input file name and output file name
        String inputFile = "bookTitles.txt";
        String ouputFile = "duplicateTitles.txt";
        
        // create HashSet which does not store duplicte values
        HashSet<String> bookTitles = new HashSet<>();
        
        
        // create arrayList which stores only duplicate bok titles
        ArrayList<String> duplicateBookTitles = new ArrayList<>();
        
        
        // now read the book titles from the bookTitles.txt
        try{
            
            // create an object Of fileReader class with the specified filename with the path
            FileReader fr = new FileReader(filePath+inputFile);
            
            // create an object of BufferedReader class for reading line from txt file
            BufferedReader br = new BufferedReader(fr);
            
            String getLine = "";
            
            System.out.println("-------------- Fetch data from the file ---------------\n");
            while((getLine = br.readLine()) != null){
                
                // add book title to the bookTitles arrayList
                if(!bookTitles.contains(getLine)){
                    
                    // diplay to the console
                    System.out.println(getLine+" readed successfully from "+filePath+inputFile);
                
                    // add to the hash set
                    bookTitles.add(getLine);
                    
                }else{
                    
                    // when HashSet does not store duplicate value then this vlue we store into the duplicateBookTitles
                    duplicateBookTitles.add(getLine);
                }
                    
            }
            
            // display duplicate book title into the console
            System.out.print("Duplicate book titles fetched from "+filePath+inputFile+" : ");
            System.out.println(duplicateBookTitles.toString());
            
            // now store it into the "duplicateTitles.txt" file
            
            // create an object of FIleWriter class for writing data into the txt file
            FileWriter write = new FileWriter(filePath+ouputFile);
            
            System.out.println("\n------------ Write Duplicate BookTitles ----------------\n");
            
            // now get each element from the duplicateBookTitles arrayList
            for(String duplicateBookTitle : duplicateBookTitles){
                
                // write into the "duplicateTitles.txt" file
                write.write(duplicateBookTitle+"\n");
                
                // print on console
                System.out.println(duplicateBookTitle+" writed succssfully into the "+filePath+ouputFile);
            }
            
            // close the writer
            write.close();
            fr.close();
            br.close();
            
            
        }catch(FileNotFoundException e){
            
            System.out.println("FILE '"+inputFile+"' IS NOT FOUND in "+filePath);
            
        } catch (IOException ex) {
            System.out.println(ex);
        }
        
        
    }
    
}

Output:-

1> input file (bookTitles.txt):-

2> console output of program

3> output file (duplicateTitles.txt):-

I hope you will understand how to fetch duplicate values using HashsSet and ArrayList.

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Thank you.