Problems w/ a HashMap

[G. Graz]

The program below takes values entered by the user and stores them into a HashMap . I am specifically having issues with option #3 " Retrieve an Employee" . All my data gets entered into the HashMap correctly , but I run option #3 I will get an incorrect result ? from the output the data displayed is the last input form the user ? When I debug the program the "value" in the map is correct with what was entered.......so if my "values" are correct and I am using the "containsvale" method , why is my result returning the last value entered by the user ? Thank you for any suggestions !

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeSet;


public class HW1 {

    public static void main(String[] args) {

    Map<String, Integer> ssnKeys = new HashMap<String, Integer>( );
    TreeSet<Employee> emps = new TreeSet<Employee>( );

        String firstName = "";
        String lastName = "";
        int SSN = 0;
        String choice;

        Scanner in = new Scanner(System.in);
                
             
        System.out.println("Welcome");
        System.out.println();
        System.out.println("Please enter selection 1-5");
        System.out.println();
        System.out.println("Add new emploee: 1");
        System.out.println("Delete an employee: 2");
        System.out.println("Retrieve an employee: 3");
        System.out.println("Print out all employees: 4");
        System.out.println("Exit: 5");
        System.out.println();


        while(in.hasNextInt()){

              
        String userInput = in.next();
        int userDecision = Integer.parseInt(userInput);

            if(userDecision == 1){

                System.out.println("Pleae Enter The Employee SSN:");
                choice = in.next();
                SSN = Integer.parseInt(choice);
               

                if (ssnKeys.containsValue(SSN)){
                    System.out.println("This Employee Is Entered Allready ");
                    break;
                    
                }

                System.out.println("Please Enter The Employee First Name:");
                firstName = in.next();
                System.out.println("Please Enter The Employee Last Name:");
                lastName = in.next();
             
               
                ssnKeys.put(firstName, SSN);
                ssnKeys.put(lastName, SSN);
                // emps.add(new Employee(lastName,firstName));
                System.out.println(ssnKeys);
                System.out.print("Please Select An Option From the Menu:");
                System.out.println();
            }
        

             else if (userDecision == 2){

                System.out.println("Please Enter an Employees SSN To Delete Record");
                choice = in.next();
                SSN = Integer.parseInt(choice);


                if (ssnKeys.containsValue(SSN)){
                    ssnKeys.remove(firstName);
                    ssnKeys.remove(lastName);
                    ssnKeys.remove(SSN);
                    //emps.remove(new Employee(lastName,firstName));
                }
                else{
                    System.out.println("There is no record of this SSN");
                }
                System.out.print("Please Select An Option From the Menu:");
                System.out.println();
            }

              else if (userDecision == 3){

                System.out.println("Please Enter an Employees SSN To Be Retrived");
                choice = in.next();
                SSN = Integer.parseInt(choice);


                if (ssnKeys.containsValue(SSN)){

                    System.out.println(SSN + "  "+firstName+" "+lastName);

                }
                else{
                    System.out.println("There is no record of this SSN");
                }
                System.out.print("Please Select An Option From the Menu:");
                System.out.println();
            }

            //  Not important to have running in regard to my question above. 

             /*
              else if (userDecision == 4){
               // TreeSet<Employee> setOfPeople = new TreeSet<Employee>();
                System.out.println("List of Employes Arranges in order by last name:");
                System.out.println();
                 for (Employee emp : emps){
                 System.out.println(emp.firstName + " " + emp.lastName);
                    }
               */

              }

 
              else if(userDecision == 5){
                System.exit(0);
            }

        }
    
    }
}

    

[Henry Wong]

so if my "values" are correct and I am using the "containsvale" method , why is my result returning the last value entered by the user ?

It is not "returning" the last value entered by the user -- you just never assigned the firstname and lastname variables, before printing them. So, basically, it is printing the last value that was assigned, which was probably when a user was added.

Henry

[Miklos Szeles]

Hi,

Fist of all I would advice to reread the documentation of Map. It stores key, value pairs. You would like to use SSN as a key but you put it as a value into the map.

ssnKeys.put(firstName, SSN);  
ssnKeys.put(lastName, SSN);  

Here you use firstname and lastname as keys, so whenever the user enters a name which's firstname or lastname is already used, then it'll change the map entry.
This mistake makes the whole program incorrect.
To answer your question:
You got the last entered name as an answer for a retrieve, since you print out the last entered name, you do nothing with the map in userDescision 3:

 if (ssnKeys.containsValue(SSN)){  
   
                     System.out.println(SSN + "  "+firstName+" "+lastName);  
   
                 } 

[Jaydeep Vaishnav]

HashMap<Integer,List<String>> would store all the information of an employee (firstname,lastname,department,desig. etc) in a list identified by unique key SSN. I don't know whether just first name and last name needs to be stored but this approach will store values in structured way and retrieving would not be a problem.

in the choice 1 (add Employee) create a list for each SSN and then store it as

List <String>employee=new ArrayList<String>();

employee.add(firstName);
employee.add(lastName);
employee.add(...);

ssnKeys.put(SSN, employee);

This way while retrieving if you try ssnKeys.containsKey(SSN), it should return the whole list. Also maintaining methods(addEmployee(),deleteEmployee() etc.) for each of the options would be a good idea.

[Miklos Szeles]

I think a better(more object oriented) aproach would be to store employee data in an Emlpoyee object.
I saw that you already have an Employee class but you haven't posted the code. I advice you to creaet a Map<Integer, Employee> to store the employees. Create an employee instance when user creates a new employee, then put it to the map using SSN as the key.

[Jaydeep Vaishnav]

Oh yes Miklos, I saw that Employee class is already there so good approach would be hashmap with SSN as key and Employee object as value.

[Billy Korando]

You are not really using the HashMap to its full potential right now. By using the containsValue() method to look up values, you are using it as little more than a glorified List. I believe someone else has suggested you should use a employee's ssn as the key and create a employee object that hold the employee's name (and probably ssn) and that that as the value. You should be pretty good then.

[Pankya Jain]

Miklos Szeles
can you provide the code for mentioned above saying???

[Jesper de Jong]

Hello Pankya Jain, welcome to the Ranch.

Please note that you are responding to a topic from almost three years ago - I'm not sure if Miklos is still here to read your request.

[Pankya Jain]

ok no problem. do you have idea who provide me java code for my problem???