mention algorithms used

List data structures used in code.

Give a description of how to use the program and expected input/output

Explain the purpose of each class developed in the program.

Programming:

For each method, give the pre and post conditions and invariant, if any

So basically Explain every line or component of the following code and run it:

import java.util.LinkedList; //taken from library files

import java.util.Scanner;

public class phonedir {

String fname; // string operations

String lname;

String phone;

public Phonedir(String fname,String lname, String phone)

{

this.fname = fname;

this.lname = lname;

this.phone = phone;

}

public static void displayMenu()

{

System.out.println("A program to keep a Phone directory");

System.out.println("a Show all records");

System.out.println("d Delete the current record");

System.out.println("f Change the first name in the current record");

System.out.println("l Change the last name in the current record");

System.out.println("n Add a new record");

System.out.println("p Change the phone number in the current record");

System.out.println("q Quit");

System.out.println("s Select a record from the record list to become the current record");

System.out.print("Enter a command from the list above(q to quit) : ");

}

public static void main(String[] args) { public loop starting LinkedList phoneList = new LinkedList();

String choice,lname,fname,phone;

Phonedir currentRecord=null;

Scanner scan = new Scanner(System.in);

do {

displayMenu();

choice = scan.nextLine();

switch(choice)

{ case "A":

case "a":

if(phoneList.size() == 0)

System.out.println("No records present");

else

{

System.out.println(" FirstName \t LastName \t Phone Number");

System.out.println("----------- \t --------- \t-------------");

for(int i=0;i

{

System.out.println(phoneList.get(i).fname+"\t "+phoneList.get(i).lname+" \t "+phoneList.get(i).phone);

}

}

break;

case "D":

case "d":

if(currentRecord == null)

System.out.println(" No Current Record");

else

{

phoneList.remove(currentRecord);

currentRecord = null;

}

break;//it will take some time

case "F":

case "f":

if(currentRecord == null)

System.out.println(" No Current Record");

else {

System.out.print(" Enter the new first name: ");

fname = scan.nextLine();

currentRecord.fname = fname;

System.out.println(" Current record is: "+currentRecord.fname + " "+currentRecord.lname+" "+currentRecord.phone);

}

break;

case "L":

case "l" :

if(currentRecord == null)

System.out.println(" No Current Record");

else {

System.out.print(" Enter the new last name: ");

lname = scan.nextLine();

phoneList.remove(currentRecord);

currentRecord.lname = lname;

boolean recordAdded = false;

for(int i=0;i

if(currentRecord.lname.compareTo(phoneList.get(i).lname)

{

phoneList.add(i, currentRecord);

recordAdded = true;

break;

}

if(!recordAdded)

phoneList.add(currentRecord);

System.out.println(" Current record is: "+currentRecord.fname + " "+currentRecord.lname+" "+currentRecord.phone);

} // ending the loop

break;

case "N":

case "n":

System.out.print(" Enter first name : ");

fname = scan.nextLine();

System.out.print(" Enter last name : ");

lname = scan.nextLine();

System.out.print(" Enter phone number : ");

phone = scan.nextLine();

currentRecord = new Phonedir(fname,lname,phone);

boolean recordAdded = false;

for(int i=0;i

if(currentRecord.lname.compareTo(phoneList.get(i).lname)

{

phoneList.add(i, currentRecord);

recordAdded = true;

break;

}

if(!recordAdded)

phoneList.add(currentRecord);

System.out.println(" Current record is: "+currentRecord.fname + " "+currentRecord.lname+" "+currentRecord.phone);

break;

case "P":

case "p":

if(currentRecord == null)

System.out.println(" No Current Record");

else {

System.out.print(" Enter the new phone number: ");

phone = scan.nextLine();

currentRecord.phone = phone;

System.out.println(" Current record is: "+currentRecord.fname + " "+currentRecord.lname+" "+currentRecord.phone);

}

break;

case "Q":

case "q": break;

case "S":

case "s":

System.out.println(" FirstName \t LastName \t Phone Number");

System.out.println("----------- \t --------- \t-------------");

for(int i=0;i

{

System.out.println(phoneList.get(i).fname+"\t "+phoneList.get(i).lname+" \t "+phoneList.get(i).phone);

}

System.out.print(" Enter first name: ");

fname = scan.nextLine();

System.out.print(" Enter last name: ");

lname = scan.nextLine();

boolean recordFound = false;

for(int i=0;i

{

if(phoneList.get(i).lname.equalsIgnoreCase(lname) && phoneList.get(i).fname.equalsIgnoreCase(fname))

{

currentRecord = phoneList.get(i);

recordFound = true;

break;

}

}

if(recordFound)

System.out.println(" Current record is: "+currentRecord.fname + " "+currentRecord.lname+" "+currentRecord.phone);

else

System.out.println(" No matching record found");

break;

default:

System.out.println(" Illegal command "); //system representations

break;

}

}while(!choice.equalsIgnoreCase("q"));

scan.close();

}

}

excuted

A program to keep a Phone directory a Show all records dDelete the current record f Change the first name in the current record 1 Change the last name in the current record n Add a new record p Change the phone number in the current record q Quit s Select a record from the record list to become the current record Enter a command from the list above (q to quit) f No Current Record A program to keep a Phone directory a Show all records d Delete the current record f Change the first name in the current record 1 Change the last name in the current record Add a new record p Change the phone number in the current record q Quit s Select a record from the record list to become the current record Enter a command from the list above (q to quit) n Enter first name: Barry Enter last name: Drake Enter phone number 770-591-8071