Java OOP Class Assignment#7

SimpleArrayList.java

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import java.util.*;
/**
 * Implementation of ArrayList using array data structure
 * Other implementation (e.g. LinkList) were record in other files
 * @author Kestin
 */
public class SimpleArrayList {
    
    /**
     * @param args the command line arguments
     */
    public int size;
    public int actual_size;
    private Integer[] arr;
    
    
    private void Callprinter(){
        for (Integer ele:arr){
            System.out.println(ele);
        }
        System.out.println("Actual size is: "+ this.actual_size);
    }
    
  
    public SimpleArrayList(int ini_size){
        this.size = ini_size;
        this.actual_size = ini_size;
        arr = new Integer[size];
        for (int i=0;i<size;i++){
            arr[i] = new Integer(0);
            //System.out.println(arr[i]);
        }
    }
    
  
    public SimpleArrayList(){
        this.size = 0;
        this.actual_size = 0;
        arr = new Integer[1];
    }
    // Default constuctor
    
    public void add(Integer value){
        if(this.actual_size==0) increaseListSize();
        // Double the array size to save the element if array is going to be full
        if(arr.length-this.actual_size <= arr.length/2){
            increaseListSize();
        }
        arr[this.actual_size++] = value;
    }
    
  
    public Integer get(int index){
        if(index < this.actual_size){
            return arr[index];
        }
        else {
            //throw new ArrayIndexOutOfBoundsException();
            return null;
        }
    }
    
    public  Integer set(int index, Integer element){
        if(index < actual_size){
            Integer oldvalue =  arr[index];
            arr[index] = element;
            return oldvalue;
        }
        else {
            //throw new ArrayIndexOutOfBoundsException();
            return null;
        }
    }
    
  
    public boolean remove(Integer index){
        if (arr[index] == null) return false;
        if(index < this.actual_size){
            Object garbage = arr[index];
            arr[index] = null;
            int tmp = index;
            while(tmp < this.actual_size-1){
                arr[tmp] = arr[tmp+1];
                arr[tmp+1] = null;
                tmp++;
            }
            this.actual_size--;
            return true;
        }
        else {
            return false;
            //throw new ArrayIndexOutOfBoundsException();
        }      
    }
    
    
    public int size(){
        return this.actual_size;
    }
  
    
    public void clear(){
        arr = new Integer[1];
        this.actual_size=0;
    }
  
    
    public boolean retainAll(SimpleArrayList l){
        int flag = 0;
        HashSet<Integer> mybag = new HashSet<Integer>();
        for (int i = 0; i < l.size(); i++) {
            mybag.add(l.get(i));
        }
        System.out.println(mybag);
        
        Integer[] original = arr.clone();
        for (int iter = 0; iter<actual_size;iter++){
            if (mybag.contains(arr[iter])) {
                continue;
            }
            else{
                remove(iter);
                flag =1;
            }
        }
        if (flag==1) {
            return true;
        }
        return false;
    }
    
  
    private void increaseListSize(){
        arr = Arrays.copyOf(arr, arr.length*2);
    }
    
  
    public static void main(String[] args) {
        
    }    
}