JAVA : COLLECTION : 9 : Implementation : ArrayList

JAVA : COLLECTION : 9 : Implementation : ArrayList

#########################  Shortcut rememberance  ################################################
get(2) - //directly get myStore[2]
add(empObj) - //directly add myStore[size++] = obj, but check need to increase before add.
remove(2) - //myStore[2] = myStore[2+1], in loop
#########################################################################

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];  //directly get myStore[2]

        } else {

            throw new ArrayIndexOutOfBoundsException();

        }

    }

     

    public void add(Object obj){

        if(myStore.length-actSize <= 5){

            increaseListSize();

        }

        myStore[actSize++] = obj; //directly add myStore[size++] = obj, but check need to increase before add.

    }

     

    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];   //2 5 1 23 14        2 5  23 14  //myStore[2] = myStore[2+1], in loop

                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