In java need help creating an application that will have usi

In java need help creating an application that will have; using the data structure, at least 5
Contact objects.

Sort by lastname :[1]
Sort by homestate :[2]
Sort by age :[3]
Enter option or 0 to end input: 0
Exiting...
Enter option or 0 to end input: 4
Invalid entry.

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

1 = Sort by last name
2 = Sort by Home State
3 = Sort by Age

Example run:
Sort by lastname :[1]
Sort by homestate :[2]
Sort by age :[3]
Enter option or 0 to end input: 1
Contact [firstname =G , lastname=A , state=WQ, age=55 ]
Contact [firstname =I , lastname=B , state=JH, age=101 ]
Contact [firstname =W , lastname=C , state=QQ, age=22 ]
Contact [firstname =A , lastname=D , state=WE, age=45 ]
Contact [firstname =A , lastname=E , state=SF, age=48 ]

I have created the class so far.
public class Contact implements Comparable<Object>{
   String firstname;
   String lastname;
   String homestate;
   Integer age;
      
   public Contact(String firstname, String lastname, String homestate, Integer age){
       this.setFirstname(firstname);
       this.setLastname(lastname);
       this.setHomestate(homestate);
       this.setAge(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 getHomestate(){
       return homestate;
   }  
   public void setHomestate(String homestate){
       this.homestate = homestate;
   }
   public Integer getAge(){
       return age;
   }
   public void setAge(Integer age){
       this.age = age;
   }
  

Solution

Please find the required program along with its output. Please see the comments against each line to understand the step.

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

OUTPUT:

A prompt for the sort by options (with 0 being exit):
1 = Sort by last name
2 = Sort by Home State
3 = Sort by Age
1
After sorting by last name:
Contact{firstname=\'G\', lastname=\'A\', homestate=\'WQ\', age=55}
Contact{firstname=\'I\', lastname=\'B\', homestate=\'JH\', age=101}
Contact{firstname=\'W\', lastname=\'C\', homestate=\'QQ\', age=22}
Contact{firstname=\'A\', lastname=\'D\', homestate=\'WE\', age=45}
Contact{firstname=\'A\', lastname=\'E\', homestate=\'SF\', age=48}
A prompt for the sort by options (with 0 being exit):
1 = Sort by last name
2 = Sort by Home State
3 = Sort by Age
2
After sorting by home state:
Contact{firstname=\'I\', lastname=\'B\', homestate=\'JH\', age=101}
Contact{firstname=\'W\', lastname=\'C\', homestate=\'QQ\', age=22}
Contact{firstname=\'A\', lastname=\'E\', homestate=\'SF\', age=48}
Contact{firstname=\'A\', lastname=\'D\', homestate=\'WE\', age=45}
Contact{firstname=\'G\', lastname=\'A\', homestate=\'WQ\', age=55}
A prompt for the sort by options (with 0 being exit):
1 = Sort by last name
2 = Sort by Home State
3 = Sort by Age
3
After sorting by age:
Contact{firstname=\'W\', lastname=\'C\', homestate=\'QQ\', age=22}
Contact{firstname=\'A\', lastname=\'D\', homestate=\'WE\', age=45}
Contact{firstname=\'A\', lastname=\'E\', homestate=\'SF\', age=48}
Contact{firstname=\'G\', lastname=\'A\', homestate=\'WQ\', age=55}
Contact{firstname=\'I\', lastname=\'B\', homestate=\'JH\', age=101}
A prompt for the sort by options (with 0 being exit):
1 = Sort by last name
2 = Sort by Home State
3 = Sort by Age
0