title: ArrayList<Integer> addAll method not adding
body: <p>Im trying to add the contents of this.array to a temp array but when i print the return value its always empty.</p>
  
  <p>Class object</p>
  
  <pre><code>import java.util.*;
  public class LetterInventory{
  
  private ArrayList&lt;Integer&gt; array;
  private int size;
  
  public LetterInventory(String input){
      size = input.length();
      array = new ArrayList&lt;Integer&gt;();
      for(int i = 0;i&lt;input.length();i++){
          array.add(i,(int)input.charAt(i));
      }
  }
  
  public LetterInventory(){
      size = 0;
      array = new ArrayList&lt;Integer&gt;();
  }
  
  public int size(){
      return size;
  }
  
  public LetterInventory add(LetterInventory other){
      LetterInventory temp = new LetterInventory();
      temp.array.addAll(array);
      return temp;
  }
  
  public String toString(){
      String result = "[";
      for(int i = 0;i&lt;=size-1;i++){
          int temp = array.get(i);
          result += (char)temp;
      }
      return result += "]";
  }
  }
  </code></pre>
  
  <p>and my Client  code</p>
  
  <pre><code>import java.util.*;
  
  public class Practice {
  public static void main (String[] args){
      LetterInventory l1 = new LetterInventory("aaa");
      LetterInventory l2 = new LetterInventory("bbb");
      System.out.println(l1);
      System.out.println(l2);
      LetterInventory sum = l1.add(l2);
      System.out.println(sum);
  }
  
  }
  </code></pre>
  
  <p>And the output is always [ ] no matter what i do. I despretly need help on this. As i've spent the vast majority of this day trying to fix this issue.</p>