Write a program to implement ArrayList.

Description:

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.

Code:

? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 package com.govindslblog.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){             increaseListSize();         }         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;                 tmp++;             }             actSize--;             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)+" ");         }     } }

Output:

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