How to transfer objects from ArrayList to LinkedList

Question

I need to transfer all the data I got in ArrayList to LinkedList and display all it all just like I did with ArrayList. I failed to display it out when I got the data transferred to LinkedList. The code is as below :

import javax.swing.*;
import java.util.*;

public class testEmployee
{
    public static void main (String [] args)
    {
        ArrayList <Employee> empArray = new ArrayList();
        LinkedList yrIncm = new LinkedList();

    Employee emp;
    int empNum;
    boolean found = true;

    empNum = Integer.parseInt(JOptionPane.showInputDialog ("How many employees information do you want to store?"));

    for (int i = 0; i < empNum; i++)
    {
        String sEmpId = JOptionPane.showInputDialog ("Please enter the employee's ID");
        String sEmpName = JOptionPane.showInputDialog ("Please enter the employee's Name");
        String sEmpPosition = JOptionPane.showInputDialog ("Please enter the employee's position");
        Double dSalary = Double.parseDouble (JOptionPane.showInputDialog ("Please enter the employee's monthly salary"));

        emp = new Employee (sEmpId, sEmpName, sEmpPosition, dSalary);

        empArray.add (emp);
    }

    System.out.println ("Employee that obtains a monthly salary more than RM 2000.00");
    System.out.println ("===========================================================");
    for (int i = 0; i<empArray.size(); i++)
    {
        if (empArray.get(i).getSalary() > 2000)
        {
            empArray.get(i).display(); // This will display the info using ArrayList
        }
    }

    System.out.println ("\nEmployee that have yearly income greater than RM 80,000");
    System.out.println ("=======================================================");
    for (int i = 0; i<empArray.size(); i++)
    {
        if ((empArray.get(i).getSalary() * 12) > 80000)
        {

            yrIncm.add (empArray.get(i)); // Is this the correct way of transferring the data? 

            System.out.println (yrIncm); // How do you print it all back? 
        }
    }

   }
}

The display() in class Employee:

public void display()
{
    System.out.println ("\nEmployee's ID : " + sEmpId);
    System.out.println ("Employee's Name : " + sEmpName);
    System.out.println ("Employee's Position : " + sEmpPosition);
    System.out.println ("Employee's Salary : RM " + df.format (dSalary));
}

I'm unable to use the method display() to print it out from the LinkedList. Any help would be appreciated

If you want to display a full list of your objects, you should not use display(). You should instead override the toString() method in Employee. You can then print a list and all its elements will be properly printed. — RealSkeptic
– RealSkeptic, Commented Sep 20, 2015 at 12:07
note: if this is not home-work that explicitly requires using linked list, then there are very few reasons to prefer this data structure over array list. — Sharon Ben Asher
– Sharon Ben Asher, Commented Sep 20, 2015 at 12:10

Marko Topolnik · Accepted Answer · 2015-09-20 12:04:07Z

1

for (int i = 0; i<empArray.size(); i++)
{
    if ((empArray.get(i).getSalary() * 12) > 80000)
    {
        LinkedList yrIncm = new LinkedList();

You create a new linked list each time and put exactly one element into it. Then you print out the one-element list and toss it away.

While the above is certainly wrong, I don't see where you imagine display() entering this picture. Your linked list never leaves the for-loop.

answered Sep 20, 2015 at 12:04

Marko Topolnik

201k31 gold badges336 silver badges455 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Nazhirin Imran Over a year ago

What a silly mistakes, I've corrected it. Now for the display(), as you can see empArray.get(i).display(); will call display() and print it out, and I've done it with Arraylist. Now I want to do the same with the LinkedList that I created and it seems that I can't call the method to print the exact same info. How do I make it possible?

Marko Topolnik Over a year ago

Java collections are iterated over using an Iterator returned from the iterator() method. A shorthand notation for that is the enhanced for loop: for (Employee emp : listOfEmployees) { emp.display(); } You should use this instead of get(i), even for ArrayList.

Amit · Accepted Answer · 2015-09-20 12:14:51Z

1

You can use LinkedList.addAll to get all the elements of the ArrayList.

LinkedList<Employee> yrIncm = new LinkedList();

yrIncm.addAll(empArray);
yrIncm.forEach(employee -> employee.display());

The problem with your code is that you are re-creating the LinkedList everytime and probably trying to call display() on a linkedlist instead of employee oobject.

answered Sep 20, 2015 at 12:14

Amit

1633 silver badges13 bronze badges

Collectives™ on Stack Overflow

How to transfer objects from ArrayList to LinkedList

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related