Java language homework I need help with. The second link at the bottom is the fi

Question

Java language homework I need help with. The second link at the bottom is the file that has to be inputed into the program !!

1. Create a linked list using the Node class that contains the first million prime numbers (primes4.txt). It should have a menu with these options:

1 = Search for a Number (let the user enter a number to search for)

2 = Add a new Number (let the user enter a number and add it to the head of the list)

3 = Delete a Number (let the user enter a number and delete it if found)

4 = Exit

class Node

{

int Data;

Node Next;

// you may want to also create a constructor that takes the Data as a parameter

Node()

{

Next = null;

}

}

http://mypccourse.com/cosc2436/primes4.txt

Explanation / Answer

import java.util.*;
import java.io.*;

class Node

{   
    public static void main(String args[])
    {
        int ch;
        String num;
        try
        {
            // Open the file that is the first
            FileInputStream fstream = new FileInputStream("primes4.txt");
            // Get the object of DataInputStream
            DataInputStream in = new DataInputStream(fstream);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            String strLine;
            //Read File Line By Line and adding it to linked list.
            LinkedList<String> linkList = new LinkedList<String>();
            while ((strLine = br.readLine()) != null)
            {
                linkList.add(strLine);
            }
            System.out.println("Please select any option.");
            System.out.println("Select 1 to search for a number.");
            System.out.println("Select 2 to add a new number.");
            System.out.println("Select 3 to delete a number");
            System.out.println("Select 4 to exit.");
            Scanner scan2 = new Scanner(System.in);
            // switch case statement to select option.
            ch = scan2.nextInt();
            switch(ch)
            {
                case 1:
                    System.out.println("Please enter no. to search.");
                    num = scanInput();
                    search(linkList, num);
                    break;
                case 2:
                    System.out.println("Please enter no. to add it to the head of list.");
                    num = scanInput();
                    add(linkList, num);
                    break;
                case 3:
                    System.out.println("Please enter no. to delete it.");
                    num = scanInput();
                    delete(linkList, num);
                    break;
                case 4:
                    break; //to quit
            }
          
            //Close the input stream
            in.close();
          
            //Modifying contents in file
            FileWriter fw = new FileWriter("primes4.txt");
            BufferedWriter out = new BufferedWriter(fw);
            for(String s : linkList)
            {
                out.write(s);
                out.write(" ");
                out.flush();
            }
            out.close();
        }
        catch (Exception e)
        {//Catch exception if any
            System.err.println("Error: " + e.getMessage());
        }
    }
    //scaning input
    public static String scanInput()
    {
        Scanner scan = new Scanner(System.in);
        return scan.nextLine();
    }
  
    //searching number
    public static void search(LinkedList<String> list, String num)
    {
        if(list.contains(num))
            System.out.println("Number " + num + " is at " + list.indexOf(num) + " position.");
        else
            System.out.println("File doesn't contain this number");
    }
  
    //adding number to list
    public static void add(LinkedList<String> list, String num)
    {
        list.addFirst(num);
    }
  
    //deleting number from list
    public static void delete(LinkedList<String> list, String num)
    {
        if(list.contains(num))
            list.remove(num);
        else
            System.out.println("File doesn't contain this number");
    }
}

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