1. Write a telephone lookup program. Read a data set of 1, 000 names and telephone numbers from a file that contains the numbers in random order. Handle lookups by name and also reverse lookups by phone number. Use a binary search for both lookups.

Kindly note that, you're to replace "at" with shift 2 as the text editor can't take the symbol

Explanation:

PhoneLookup.java

import java.io.FileReader;

import java.io.IOException;

import java.util.Scanner;

public class PhoneLookup

{

  public static void main(String[] args) throws IOException

  {

     Scanner in = new Scanner(System.in);

     System.out.println("Enter the name of the phonebook file: ");

     String fileName = in.nextLine();

     LookupTable table = new LookupTable();

     FileReader reader = new FileReader(fileName);

     table.read(new Scanner(reader));

     boolean more = true;

     while (more)

     {

        System.out.println("Lookup N)ame, P)hone number, Q)uit?");

        String cmd = in.nextLine();

        if (cmd.equalsIgnoreCase("Q"))

           more = false;

        else if (cmd.equalsIgnoreCase("N"))

        {

           System.out.println("Enter name:");

           String n = in.nextLine();

           System.out.println("Phone number: " + table.lookup(n));

        }

        else if (cmd.equalsIgnoreCase("P"))

        {

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

           String n = in.nextLine();

           System.out.println("Name: " + table.reverseLookup(n));

        }

     }

  }

}

LookupTable.java

import java.util.ArrayList;

import java.util.Collections;

import java.util.Scanner;

/**

  A table for lookups and reverse lookups

*/

public class LookupTable

{

  private ArrayList<Item> people;

  /**

     Constructs a LookupTable object.

  */

  public LookupTable()

  {

      people = new ArrayList<Item>();

  }

  /**

     Reads key/value pairs.

     "at"param in the scanner for reading the input

  */

  public void read(Scanner in)

  {

     while(in.hasNext()){

         String name = in.nextLine();

         String number = in.nextLine();

         people.add(new Item(name, number));

     }

  }

  /**

     Looks up an item in the table.

     "at"param k the key to find

     "at"return the value with the given key, or null if no

     such item was found.

  */

  public String lookup(String k)

  {

     String output = null;

     for(Item item: people){

         if(k.equals(item.getName())){

             output = item.getNumber();

         }

     }

     return output;

  }

  /**

     Looks up an item in the table.

     "at"param v the value to find

     "at"return the key with the given value, or null if no

     such item was found.

  */

  public String reverseLookup(String v)

  {

      String output = null;

         for(Item item: people){

             if(v.equals(item.getNumber())){

                 output = item.getName();

             }

         }

         return output;

  }

}

Item.java

public class Item {

  private String name, number;

  public Item(String aName, String aNumber){

      name = aName;

      number = aNumber;

  }

  public String getName(){

      return name;

  }

  public String getNumber(){

      return number;

  }

}

input.txt

Abbott, Amy

408-924-1669

Abeyta, Ric

408-924-2185

Abrams, Arthur

408-924-6120

Abriam-Yago, Kathy

408-924-3159

Accardo, Dan

408-924-2236

Acevedo, Elvira

408-924-5200

Acevedo, Gloria

408-924-6556

Achtenhagen, Stephen

408-924-3522

Kindly check the attached output image below.