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Program: Write a program to implement ArrayList.

Write a program to implement your own ArrayList class. It should
contain add(), get(), remove(), size() methods. Use dynamic array logic.
It should increase its size when it reaches threshold.

package com.java2novice.algos;

import java.util.Arrays;

public class MyArrayList {

        private Object[] myStore;
        private int actSize = 0;
        public MyArrayList(){
                myStore = new Object[10];
        public Object get(int index){
                if(index < actSize){
                        return myStore[index];
                } else {
                        throw new ArrayIndexOutOfBoundsException();
        public void add(Object obj){
                if(myStore.length-actSize <= 5){
                myStore[actSize++] = obj;
        public Object remove(int index){
                if(index < actSize){
                        Object obj = myStore[index];
                        myStore[index] = null;
                        int tmp = index;
                        while(tmp < actSize){
                                myStore[tmp] = myStore[tmp+1];
                                myStore[tmp+1] = null;
                        return obj;
                } else {
                        throw new ArrayIndexOutOfBoundsException();
        public int size(){
                return actSize;
        private void increaseListSize(){
                myStore = Arrays.copyOf(myStore, myStore.length*2);
                System.out.println("\nNew length: "+myStore.length);
        public static void main(String a[]){
                MyArrayList mal = new MyArrayList();
                mal.add(new Integer(2));
                mal.add(new Integer(5));
                mal.add(new Integer(1));
                mal.add(new Integer(23));
                mal.add(new Integer(14));
                for(int i=0;i<mal.size();i++){
                        System.out.print(mal.get(i)+" ");
                mal.add(new Integer(29));
                System.out.println("Element at Index 5:"+mal.get(5));
                System.out.println("List size: "+mal.size());
                System.out.println("Removing element at index 2: "+mal.remove(2));
                for(int i=0;i<mal.size();i++){
                        System.out.print(mal.get(i)+" ");

2 5 1 23 14 
New length: 20
Element at Index 5:29
List size: 6
Removing element at index 2: 1
2 5 23 14 29 
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List Of All Interview Programs:

  1. Remove last node of the Linked List
  2. Identify middle element of a Linked List
  3. Identify given LinkedList is a palindrom or not using Stack.
  4. Remove duplicates from sorted linked list
  5. Find Nth node from the end of Linked List
  6. Identify loop/cycle in a LinkedList.
  7. Find length of a loop in a LinkedList.
  8. Detect and remove loop in a LinkedList.
  9. How to reverse Singly Linked List?
  10. Check if given Linked List is a Circular Linked List or not.
  11. Find out duplicate number between 1 to N numbers.
  12. Find out middle index where sum of both ends are equal.
  13. Write a singleton class.
  14. Write a program to create deadlock between two threads.
  15. Write a program to reverse a string using recursive algorithm.
  16. Write a program to reverse a number.
  17. Write a program to convert decimal number to binary format.
  18. Write a program to find perfect number or not.
  19. Write a program to implement ArrayList.
  20. Write a program to find maximum repeated words from a file.
  21. Wrie a program to find out duplicate characters in a string.
  22. Write a program to find top two maximum numbers in a array.
  23. Write a program to sort a map by value.
  24. Write a program to find common elements between two arrays.
  25. How to swap two numbers without using temporary variable?
  26. Write a program to print fibonacci series.
  27. Write a program to find sum of each digit in the given number using recursion.
  28. Write a program to check the given number is a prime number or not?
  29. Write a program to find the given number is Armstrong number or not?
  30. Write a program to convert binary to decimal number.
  31. Write a program to check the given number is binary number or not?
  32. Write a program for Bubble Sort in java.
  33. Write a program for Insertion Sort in java.
  34. Write a program to implement hashcode and equals.
  35. How to get distinct elements from an array by avoiding duplicate elements?
  36. Write a program to get distinct word list from the given file.
  37. Write a program to get a line with max word count from the given file.
  38. Write a program to convert string to number without using Integer.parseInt() method.
  39. Write a program to find two lines with max characters in descending order.
  40. Write a program to find the sum of the first 1000 prime numbers.
  41. Find longest substring without repeating characters.
  42. Write a program to remove duplicates from sorted array.
  43. How to sort a Stack using a temporary Stack?
  44. Write a program to print all permutations of a given string.
  45. Implement Binary Search Tree (BST)
  46. Find min and max value from Binary Search Tree (BST)
  47. Find height of a Binary Search Tree (BST)
  48. Implement Binary Search Tree (BST) Level order traversal (breadth first).
  49. Implement Binary Search Tree (BST) pre-order traversal (depth first).
  50. Implement Binary Search Tree (BST) in-order traversal (depth first).
  51. Implement Binary Search Tree (BST) post-order traversal (depth first).
  52. How to check the given Binary Tree is Binary Search Tree (BST) or not?
  53. How to delete a node from Binary Search Tree (BST)?
  54. Write a program to find common integers between two sorted arrays.
  55. Write a program to find given two trees are mirror or not.
  56. HackerRank stack problem - Find maximum element.
  57. HackerRank stack problem - Balanced Brackets.
  58. HackerRank stack problem - Equal Stacks.
  59. HackerRank stack problem - Game Of Two Stacks.
Knowledge Centre
Inner class and Anonymous class
Inner class: classes defined in other classes, including those defined in methods are called inner classes. An inner class can have any accessibility including private.

Anonymous class: Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors.
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It is amazing what you can accomplish if you do not care who gets the credit.
-- Harry Truman

About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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