Write an application that will have; using the data structure of your choice, at

Question

Write an application that will have; using the data structure of your choice, at least 5 Contact objects that will be sorted using Comparators. These are the following requirements:

- A prompt for the sort by options (with 0 being exit):

Sort by lastname :[1]

Sort by home state :[2]

Sort by age :[3]

Enter option or 0 to end input: 0

Exiting...

- 1= Sort by last name

- 2 = Sort by Home State

- 3 = Sort by Age

- Also regonize an invalid entry

Sort by lastname :[1]

Sort by home state :[2]

Sort by age :[3]

Enter option or 0 to end input: 4

Invalid Entry

/*
* The Contact class will have 3 properties:
*        firstname - String
*        lastname - String
*        homestate - String
*        age - Integer
*/

public class Contact {

}

import java.util.ArrayList;

public class TestSortOptions {

   public static void main(String[] args) {
       ArrayList<Contact> contacts = initializeContactsArray();
promptForOption(contacts);
   }

/*
* Data Initialization
*/
  
private static ArrayList<Contact> initializeContactsArray() {
// TODO: Initialize an array of Student objects
return null;
}
  
/*
* Prompt for the user to enter their option from the keyboard
*
* 1 = Sort by last name
* 2 = Sort by Home State
* 3 = Sort by Age
* 0 = End input and exit/terminate the application
*
*/
  
private static void promptForOption(ArrayList<Contact> contacts) {
// TODO: Prompt and accept option input
}

/*
* Display the Contact information sorted by using the selected option from
* the above "promptForOption" method result
*/
  
private static void displayContacts(ArrayList<Contact> contacts) {
// TODO: Display the contents of the Contacts Array
}

}

Explanation / Answer

//TestSortOptions.java
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class TestSortOptions {

   public static void main(String[] args)
   {
      
       //Create an instance of ArrayList of type Contact
       ArrayList<Contact> studentsList = initializeContactsArray();
      
       //Create an instance of Scanner class
       Scanner scanner = new Scanner(System.in);
       boolean repeat=true;
      
       String choice="";      
       //Loop continues until user enters n to stop
       while(repeat)
       {
           promptForOption(studentsList);
           System.out.println("Do you want to continue [y or n :]");
           choice=scanner.nextLine();
          
           if(choice.charAt(0)=='n'||choice.charAt(0)=='N')
               repeat=false;
       }
   }

  
   /*
   * Method to intialize the student list with contac objects
   * */
   private static ArrayList<Contact> initializeContactsArray()
   {
       ArrayList<Contact> studentsList = new ArrayList<Contact>();
       studentsList.add(new Contact("Bill", "Bose", "NY", 46));
       studentsList.add(new Contact("Morry", "Apple", "KY", 23));
       studentsList.add(new Contact("Angel", "Bradit", "NE", 56));
       studentsList.add(new Contact("Murali", "Mutta", "LD", 35));
       studentsList.add(new Contact("Hani", "Hunt", "IE", 67));

       return studentsList;
   }

  
   /*
   * Method to prompt user to select a choice
   * */
   private static void promptForOption(ArrayList<Contact> contacts) {
       Scanner scanner = new Scanner(System.in);

       System.out.println("Options Sort by Last Name:[1] ");
       System.out.println("Sort by Home State: [2]");
       System.out.println("nSort by Age:        [3]");
       System.out.println("Exit Application:   [0]");
       System.out.println("Please enter your choice:");
       int answer = scanner.nextInt();

       switch(answer)
       {
       case 1:
           Collections.sort(contacts, Contact.sortByLastName);
           break;
       case 2:          
           Collections.sort(contacts, Contact.sortByStateName);
           break;
       case 3:
           Collections.sort(contacts, Contact.sortByageName);
           break;
       case 0:
           System.exit(0);
       default :
           System.out.println("Invalid choice");
       }
       //calling method displayContacts
       displayContacts(contacts);
   }
  
  
   /*
   * displayContacts that display the contacts to console.
   * */
   private static void displayContacts(ArrayList<Contact> contacts) {

       for (Contact contact : contacts) {
           System.out.println(contact);
       }

   }
}

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

/**
* The class Contact contains methods to sort
* by last name, state and age.
* */
//Contact.java
import java.util.Comparator;
public class Contact
{
  
   //instance variables of class Contact
   private String firstName;
   private String lastName;
   private String state;
   private Integer age;

  
   //Constructor that takes first name, last name, state and age
   public Contact(String firstName, String lastName,
           String state, Integer age) {

       this.firstName = firstName;
       this.lastName = lastName;
       this.state = state;
       this.age=age;
   }

   public String getFirstName() {
       return firstName;
   }

   public void setFirstName(String firstName) {
       this.firstName = firstName;
   }

   public String getLastName() {
       return lastName;
   }

   public void setLastName(String lastName) {
       this.lastName = lastName;
   }

   public String getState() {
       return state;
   }

   public void setState(String state) {
       this.state = state;
   }

   public Integer getAge() {
       return age;
   }

   public void setAge(int age) {
       this.age = age;
   }

   //Comparator that sorts the last name
   public static Comparator<Contact> sortByLastName = new Comparator<Contact>() {

       public int compare(Contact c1, Contact c2) {
           String cname1 = c1.getLastName().toUpperCase();
           String cname2 = c2.getLastName().toUpperCase();

           return cname1.compareTo(cname2);
       }
   };

   //Comparator that sort two contacts by state
   public static Comparator<Contact> sortByStateName = new Comparator<Contact>() {

       public int compare(Contact s1, Contact s2) {
           String state1 = s1.getState().toUpperCase();
           String state2 = s2.getState().toUpperCase();

           return state1.compareTo(state2);
       }
   };
   //Comparator that sort two contacts by age
   public static Comparator<Contact> sortByageName = new Comparator<Contact>() {
       public int compare(Contact s1, Contact s2) {
           int age1 = s1.getAge();
           int age2 = s2.getAge();
           return age1 - age2;
       }
   };
   //Returns the string representation of Contact
   public String toString() {
       return String.format("%-10s%-10s%-10s%-5d", firstName,lastName,state,age);
   }
}

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

Sample output:

Options
Sort by Last Name:[1]
Sort by Home State: [2]
nSort by Age:        [3]
Exit Application:   [0]
Please enter your choice:
1
Morry     Apple     KY        23
Bill      Bose      NY        46
Angel     Bradit    NE        56
Hani      Hunt      IE        67
Murali    Mutta     LD        35
Do you want to continue [y or n :]
y
Options
Sort by Last Name:[1]
Sort by Home State: [2]
nSort by Age:        [3]
Exit Application:   [0]
Please enter your choice:
2
Hani      Hunt      IE        67
Morry     Apple     KY        23
Murali    Mutta     LD        35
Angel     Bradit    NE        56
Bill      Bose      NY        46
Do you want to continue [y or n :]
y
Options
Sort by Last Name:[1]
Sort by Home State: [2]
nSort by Age:        [3]
Exit Application:   [0]
Please enter your choice:
3
Morry     Apple     KY        23
Murali    Mutta     LD        35
Bill      Bose      NY        46
Angel     Bradit    NE        56
Hani      Hunt      IE        67
Do you want to continue [y or n :]
n

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