Write a telephone lookup program. Read a data set of 1,000 names and telephone numbers from a file (directory. txt) 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. A driver program and templates have been created for you.

Here is the JAVA program:

Items.java

public class Item {  // Item class

private String name, ph_num;  // class data members name to hold the name and ph_num stores the telephone numbers

public Item(String fullName, String PhoneNo){  //constructor of Item class , so fields full name and ph_num can be initialized when the object is created

name = fullName;  // holds the name field

ph_num = PhoneNo;}  //holds the telephone number

public String getFullName(){  // accessor method to get access to the name field

return name;}  //returns the name from directory

public String getPhoneNo(){  //accessor method to get access to the ph_nujm field

return ph_num; } } //returns the telephone number

Explanation:

LookupTable.java

public class LookupTable{  //class name

private ArrayList<Item> data;  // dynamic array list named data of Item class. This array list stores the names and telephone numbers from file

public LookupTable(){  //default constructor

data = new ArrayList<Item>();}  // creates an array list of Item type which holds the names and phone numbers

public void read(Scanner in){  // Scanner class object is created and this class is used to read input and the method reads the names and phone numbers

while(in.hasNext()){  // the loop moves through each line of the file. scanner class method hasNext checks for the tokens in the input

String name = in.nextLine();  // scans for the name in the input

String ph_num = in.nextLine();  //scans for the phone numbers in the input

data.add(new Item(name, ph_num));}}  // adds the names and phone number in to the Array list

public String lookup(String k){  //method looks up for an item in the table.  param k is the key to find . returns the value with the given key, or null if no       such item was found

String result = null;  //result initialized to to null

for(Item item: data){  //creates Item object and traverses the array list for each item i.e. name or phone numbers

if(k.equals(item.getFullName())){  //access the getFullName method through object item and checks if that name matches the key to find.

result = item.getPhoneNo();}}  //gets the corresponding phone number and assigns it to result variable

return result;}  //returns the result containing the phone number

public String reverseLookup(String v){  //Looks up an item in the table. param v is the value to find . returns the key with the given value, or null if no  such item was found. This method performs the lookup through phone number

String result = null;  //result is set to null to start

for(Item item: data){  //Traversing list through the for each item in data  

if(v.equals(item.getPhoneNo())){  //if the value of v is equal to the phone number accessed by using accessor method and object item

result = item.getFullName();}}  //accesses the corresponding name of that phone number and assigns it to the result

return result;}}  //returns the result                                

The data from directory file which contains the number and names. The LookupTable class has a method lookup which handles the lookups by names and the method reverseLookup that handles the lookups by phone number.