Please help me complete the following java programming tasks. I need a correct answer as a reference for me to correct my own tasks. Thank you very much.

In this exercise you need to complete these additional features one by one for the extended phone book program. Here are the tasks in the exercise:

Checking for duplicated entry when a new phone number is added$($plz finish it in this question$)$

Finding a phone number entry by name$($no need to finish$)$

Delete a phone number entry by name$($no need to finish$)$

Here is a part of the uncompleted java code given in the task. Please finish this part:

public class PhoneBook

$\{$

$//$ Prepare a scanner for reading inputs

Scanner scanner $=$ new Scanner$($System$.$in$)$;

$//$ Show the main menu of the program

public void mainmenu$()$

$\{$

System.out.println$("$Welcome to the phone book program."$)$;

System.out.println$()$;

String choice;

do $\{$

$//$ Print the main menu

System.out.println$("$Please choose one of the following:"$)$;

System.out.println$()$;

System.out.println$("1)$ Add New Phone Number"$)$;

System.out.println$("2)$ List Phone Numbers"$)$;

System.out.println$("3)$ Find Phone Number by Name"$)$;

System.out.println$("4)$ Delete Phone Number by Name"$)$;

System.out.println$("5)$ Quit"$)$;

System.out.println$()$;

System.out.print$("$Please enter $1,2,3,4$ or $5$: $")$;

$//$ Get the selection from the user

choice $=$ scanner.next$()$;

$//$ Based on the selection run the appropriate method

switch $($choice$)\{$

case $"1"$:

addNumber$()$;

break;

case $"2"$:

listNumbers$()$;

break;

case $"3"$:

findNumberByName$()$;

break;

case $"4"$:

deleteNumberByName$()$;

break;

$\}$

System.out.println$()$;

$\}$ while $(!$choice.equals$("5"))$;

System.out.println$("$Bye$!")$;

$\}$

$//$ Check whether the name exists in the current phone book

public boolean exists$($String name$)\{$

$//$

$//$ Task $1-$ Checking for duplicated new entry

$//$

$//$ Get the path of the text file

$//$ Use a BufferedReader to read the data one by one

$//$ For each data line create a PhoneBookEntry

$//$ If the name in the PhoneBookEntry is equal to the input name

$//$ return true

$//$ Return false if nothing matches the input name

return false;

$\}$

$//$ Add a new entry to the phone book

public void addNumber$()\{$

$//$ Get the name

System.out.print$("$Please enter the name: $")$;

String name $=$ scanner.next$()$;

$//$ Get the number

System.out.print$("$Please enter the number: $")$;

String number $=$ scanner.next$()$;

$//$ Check whether the name already exists, if so$,$

$//$ print a message and exit the method

if $($exists$($name$))\{$

System.out.println$("$Phone number entry already exists!"$)$;

return;

$\}$

$//$ Get the path of the text file

Path path $=$ Paths.get$("$phonebook$.$txt$")$;

try $\{$

$//$ Get a BufferedWriter from the file

BufferedWriter writer $=$

Files.newBufferedWriter$($path$,$ Charset.defaultCharset$(),$

StandardOpenOption.APPEND$)$;

$//$ Create a new phone book entry from the data

PhoneBookEntry entry $=$ new PhoneBookEntry$($name$,$ number$)$;

$//$ Add a new phone number in a line

writer.write$($entry$.$toLine$())$;

writer.newLine$()$;

$//$ Close the writer

writer.close$()$;

$\}$

catch $($Exception e$)\{$

System.out.println$("$I have some problems writing the file!"$)$;

$\}$

$\}$

In this exercise, each phone number entry is still stored as a separate line. However, the name and the phone number of one entry are separated by a colon, without a space. You can see the format of the phone book from the given phonebook.txt$,$ as shown below:

CSO:$2358-6333$

FMO:$2358-6421$

FO:$2358-6418$

HRO:$2358-6580$

ITSC:$2358-6188$

SAO:$2358-0842$

Some errors are caused by the exists method, which has been used in the above code, is empty.

The first task is finishing the exists method so that the code inside the addNumber method works:

if $($exists$($name$))\{$

System.out.println$("$Phone number entry already exists!"$)$;

return;

$\}$