Question

Java. Given an input file with each line representing a record of data and the first token (word) being the key that the file is sorted on, we want to load it and output the line number and record for any duplicate keys we encounter. Remember we are assuming the file is sorted by the key and we want to output to the screen the records (and line numbers) with duplicate keys. We are given a text file and have to use the scanner class to lod it

Your task is to

• create a FindDuplicates class with the following:

  • Declaration of an instance variables for the String filename

  • non-default Constructor - creates an object for user passed filename argument

  • Accessor methods return the value of each instance variable

  • Mutator methods that allows th user to set each instance variable (no validation required),

  • a "getDuplicates()" method that reads from the file (until end-of-file) using Scanner class, finds duplicate records based on the first token on each line (the key), and returns as a String the record number and entire duplicate record one to a line (see above Sample output)

  • • toString() - returns a String message with the value of the instance variable

Sample Output

Enter File Name: input1.txt

FileName:input1.txt

DUPLICATES

12 102380 CS US W 2.8 3.267 125

14 102395 PPCI US W 2.769 2.5 115

25 102567 PPCI US W 3.192 3.412 112

35 102912 CS US Z 3.81 3.667 88

44 103087 CS US Z 2.956 2.688 90

76 103944 CS US W 3.134 3.294 134

77 103944 CS US W 3.698 3.7 94

86 104046 CS US W 2.863 3.133 65

88 104047 CS US W 3.523 3.524 77

89 104047 CS US O 3.825 3.824 49

91 104048 CS US W 3.071 3 94

92 104048 CS US W 3.114 3.111 44

93 104048 CS US W 3.375 3.6 71

Press any key to continue . . .

Answer 1

Please find the required program along with the comments and output:

NOTE: I'm taking only a sample file that is created with the available records only shown in question, and made duplicated some records.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        String fileName = "C:\\Users\\rishi\\IdeaProjects\\Test\\src\\input1.txt";  //input file path

        //creating an object for the FindDuplicates class
        FindDuplicates duplicates = new FindDuplicates(fileName);

        //get the duplicates
        String dups = duplicates.getDuplicates();

        //print the result
        System.out.println("DUPLICATES");
        System.out.println(dups);
    }

}


class FindDuplicates {

    private String filename;

    //non-default Constructor - creates an object for user passed filename argument
    public FindDuplicates(String filename) {
        this.filename = filename;
    }

    //Accessor methods return the value of each instance variable
    public String getFilename() {
        return filename;
    }

    //Mutator methods that allows th user to set each instance variable
    public void setFilename(String filename) {
        this.filename = filename;
    }

    public String getDuplicates() {
        String dups = "";   //to store duplicate records
        ArrayList<String> keys = new ArrayList<>();     //to store the non duplicate keys
        try {
            Scanner scanner = new Scanner(new File(filename));  //scanner to read from file
            while (scanner.hasNext()) {     //read until end of file
                String line = scanner.nextLine();   //read the current line
                String[] split = line.split(" ");   //split the current line with space
                String key = split[0].trim();     //get the first word as key
                if(keys.contains(key)) {    //if the key already contains in the list
                    dups = dups + " " + line + "\n";    //if the key is a duplicate, then store the line to return, else continue
                }else {
                    keys.add(key);  //if key is not found in list, then add that key to the list
                }
            }
        }catch (FileNotFoundException fne){
            System.out.println("File not found!");
        }
        return dups;
    }

    @Override
    public String toString() {
        return filename;
    }
}

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OUTPUT: