ArrayList custom implementation - add, get, remove Employee object in java

In this post i will be explaining how to  add, get, remove Employee object in custom ArrayList.

Methods used in custom ArrayList-
public void add(E value)
Add objects in ArrayListCustom
public E get(int index)
Method returns element on specific index.
public Object remove(int index)
Method returns removedElement on specific index, else it throws IndexOutOfBoundException if index is negative or greater than size of size.
public void display()
-Method displays all objects in ArrayListCustom.
-Insertion order is guaranteed.
private void ensureCapacity()
Method increases capacity of list by making it double.







Full Program/SourceCode to add, get, remove Employee object in custom ArrayList.
package com.ankit;
import java.util.Arrays;
class Employee {
   private String id;
   private String name;
  
   /**
   * Employee constructor
   */
   public Employee(String id, String name) { // constructor
          this.id = id;
          this.name = name;
   }
   @Override
   public String toString() {
          return "Employee[id=" + id + ", name=" + name + "] ";
   }
}

/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
/**
* @author AnkitMittal
* Copyright (c), AnkitMittal . All Contents are copyrighted and must not be reproduced in any form.
* This class provides custom implementation of ArrayList(without using java api's)
* Insertion order of objects is maintained.
* Implementation allows you to store null as well.
* @param <E>
*/
class ArrayListCustom<E> {
  
 private static final int INITIAL_CAPACITY = 10;
 private Object elementData[]={};
 private int size = 0;
 /**
 * constructor.
 */
 public ArrayListCustom() {
   elementData = new Object[INITIAL_CAPACITY];
 }
 /**
  * method adds elements in ArrayListCustom.
  */
 public void add(E e) {
   if (size == elementData.length) {
     ensureCapacity(); //increase current capacity of list, make it double.
   }
   elementData[size++] = e;
 }
 /**
  * method returns element on specific index.
  */
 @SuppressWarnings("unchecked")
 public E get(int index) {
   if ( index <0 || index>= size) { //if index is negative or greater than size of size, we throw Exception.
     throw new IndexOutOfBoundsException("Index: " + index + ", Size " + index);
   }
   return (E) elementData[index]; //return value on index.
 }
 /**
  * method returns removedElement on specific index.
  * else it throws IndexOutOfBoundException if index is negative or greater than size of size.
  */
 public Object remove(int index) {
   if ( index <0 || index>= size) { //if index is negative or greater than size of size, we throw Exception.
     throw new IndexOutOfBoundsException("Index: " + index + ", Size " + index);
   }
  
   Object removedElement=elementData[index];
   for(int i=index;i<size;i++){
      elementData[i]=elementData[i+1];
   }
   size--;   //reduce size of ArrayListCustom after removal of element.
  
   return removedElement;
 }
 /**
  * method increases capacity of list by making it double.
  */
 private void ensureCapacity() {
   int newIncreasedCapacity = elementData.length * 2;
   elementData = Arrays.copyOf(elementData, newIncreasedCapacity);
 }
 /**
  * method displays all the elements in list.
  */
 public void display() {
    System.out.print("Displaying list : ");
    for(int i=0;i<size;i++){
           System.out.print(elementData[i]+" ");
    }
 }
}

/** Copyright (c), AnkitMittal  JavaMadeSoEasy.com */
/**
* Main class to test ArrayListCustom functionality.
*/
public class ArrayListEmployee {
  
    public static void main(String...a) {
          ArrayListCustom<Employee> list = new ArrayListCustom<Employee>();
   list.add(new Employee("1", "sam"));
   list.add(new Employee("2", "amy"));
   list.add(new Employee("3", "wil"));
   list.add(new Employee("4", "cat"));
   list.add(new Employee("1", "sam"));
   list.add(new Employee("2", "amy"));
   list.add(null);
  
   list.display();
   System.out.println("\nelement at index "+1+" = "+list.get(1));
   System.out.println("element removed from index "+1+" = "+list.remove(1));
  
   System.out.println("\nlet's display list again after removal at index 1");
  
   list.display();
  
   //list.remove(11); //will throw IndexOutOfBoundsException, because there is no element to remove on index 11.
   //list.get(11);   //will throw IndexOutOfBoundsException, because there is no element to get on index 11.
  
    }
  
}
/*Output
Displaying list : Employee[id=1, name=sam]  Employee[id=2, name=amy]  Employee[id=3, name=wil]  Employee[id=4, name=cat]  Employee[id=1, name=sam]  Employee[id=2, name=amy]  null
element at index 1 = Employee[id=2, name=amy]
element removed from index 1 = Employee[id=2, name=amy]
let's display list again after removal at index 1
Displaying list : Employee[id=1, name=sam]  Employee[id=3, name=wil]  Employee[id=4, name=cat]  Employee[id=1, name=sam]  Employee[id=2, name=amy]  null
*/



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