Question

Hello, I needed help on the following

In Java:

Note that if you intend to append data to the end of a file, you need to create an instance of the "FileWriter" class rather than the "File" class:

FileWriter fwriter = new FileWriter("RunningList.txt", true);
PrintWriter outfile = new PrintWriter(fwriter);

Remember that PrintWriter objects can throw an exception, so make sure to amend your main method header with the clause "throws IOException".

(Cannot use try-catch, must include clause "throws IOException")

Write a program that asks the user to enter a filename that will store a list of names to invite to a party. Check to ensure that file doesn't exist; if it does, give the user an error message and ask them to re-run the program. Then ask the user how many names they'd like to add to the running list of names of party guests. Have them input that many names from the console, and write those to an external file. Then close the external file.

Then present the user with a menu:

• Add more guests (append to the file)
• Create new guest list (overwrite the file)
• Create new guest list (in a new file)
• Quit

If they select "add more guests", open the file in append mode, ask the user how many guests to add to the list, and then write those to the file.

If they select "create new guest list/overwrite", ask them how many names to add, and overwrite the existing file.

If they select "new guest list/new file", ask them for a new filename. Check that this file doesn't already exist; if it does, give the user an error and ask them for a new filename. Then ask how many names to add, and create/write to this new file.

Present this menu in a loop until the user elects to quit.

***GUEST LIST GENERATOR***
Enter a filename for the guest list: g.txt
How many guests do you want to add to the guest list? 2
Enter guest #1: abc
Enter guest #2: def
Enter:
        1: Add names to the guest list
        2: Create new guest list (overwrite old list)
        3: Create new guest list (new list)
        4: Quit
        Your choice: 1
Adding to the current list list...
How many guests do you want to add to the guest list? 2
Enter guest #1: ghi
Enter guest #2: jkl
Enter:
        1: Add names to the guest list
        2: Create new guest list (overwrite old list)
        3: Create new guest list (new list)
        4: Quit
        Your choice: 3
Creating new guest list...
Enter a new filename: h.txt
How many guests do you want to add to the guest list? 3
Enter guest #1: mno
Enter guest #2: pqr
Enter guest #3: stu
Enter:
        1: Add names to the guest list
        2: Create new guest list (overwrite old list)
        3: Create new guest list (new list)
        4: Quit
        Your choice: 4
Program ending.

---------------------------------------------------------

Thank you so much!

Answer 1

PROGRAM:

import java.io.*;
import java.util.*;
class Test
{
   public static void main(String[] args) throws IOException
   {
       Scanner sc=new Scanner(System.in);
       String filename="",guestname="",filename1="";
       int n,i=0;
       System.out.print("Enter a filename for the guest list:");
       filename=sc.nextLine();         //taking filename from user
       FileWriter writer = new FileWriter(filename);
       BufferedWriter fwriter = new BufferedWriter(writer);
       System.out.print("How many guests do you want to add to the guest list?");
       n=sc.nextInt();     //reading number of guest names
       sc.nextLine();
       for(i=0;i<n;i++)
       {
           System.out.print("Enter guest #"+(i+1)+":");
           guestname=sc.nextLine();     //reading guest names
           fwriter.write(guestname);     //writer names to the file
           fwriter.newLine();
       }
       fwriter.flush();
       fwriter.close();
       int ch=0,k=0;
       while(true)
       {
           System.out.println("Enter:");
           System.out.println("\t"+"1: Add names to the guest list");
           System.out.println("\t"+"2: Create new guest list (overwrite old list)");
           System.out.println("\t"+"3: Create new guest list (new list)");
           System.out.println("\t"+"4: Quit");
           System.out.print("\t"+"Your choice:");
           ch=sc.nextInt();
           switch(ch)
           {
               case 1:         //logic for appending guest names to the file
                   FileWriter fwriter1 = new FileWriter(filename, true);
                   PrintWriter outfile = new PrintWriter(fwriter1);
                   System.out.println("Adding to the current list list...");
                   System.out.print("How many guests do you want to add to the guest list?");
                   n=sc.nextInt();
                   sc.nextLine();
                   for(i=0;i<n;i++)
                   {
                       System.out.print("Enter guest #"+(i+1)+":");
                       guestname=sc.nextLine();
                       outfile.println(guestname);
                   }
                   outfile.close();

                   break;
               case 2:     //logic for overwriting guestnames with new guestnames
                   FileOutputStream fout=new FileOutputStream(filename);
                   PrintStream pout=new PrintStream(fout);  
                   System.out.print("How many guests do you want to add to the guest list?");
                   n=sc.nextInt();
                   sc.nextLine();
                   for(i=0;i<n;i++)
                   {
                       System.out.print("Enter guest #"+(i+1)+":");
                       guestname=sc.nextLine();
                       pout.println(guestname);
                   }
                   pout.close();
                   break;  
               case 3:         //logic for creating new file and adding guests to that file
                   sc.nextLine();
                   System.out.print("Enter a filename for the guest list:");
                   filename1=sc.nextLine();
                   while(filename1.equals(filename))
                   {
                       System.out.println("File name already exists:");
                       System.out.println("Enter another file name:");
                       filename1=sc.nextLine();
                   }
                   File f=new File(filename1);
                   PrintStream fileStream = new PrintStream(f);
                   System.out.print("How many guests do you want to add to the guest list?");
                   n=sc.nextInt();
                   sc.nextLine();
                   for(i=0;i<n;i++)
                   {
                       System.out.print("Enter guest #"+(i+1)+":");
                       guestname=sc.nextLine();
                       fileStream.println(guestname);
                   }
                   fileStream.close();
                   break;
               case 4:      //quitting from program
                   System.out.println("Program ending:");
                   k=1;
                   break;  
               default:
                   System.out.println("Enter valid option");

           }
           if(k==1)
           {
               break;       //terminating the program if k==1
           }

       }
   }
}

CONSOLE OUTPUT:

FILEOUTPUT: