Collection Interface Java
<pre><code>import java.util.*;

public class ArrayListDemo{
  public static void main(String[] args) {
    ArrayList&lt;Object&gt; arl=new ArrayList&lt;Object&gt;();
    Integer i1=new Integer(10);
    Integer i2=new Integer(20);
    Integer i3=new Integer(30);
    Integer i4=new Integer(40);

arl.add(i1);
arl.add(i2);
arl.add(s1);
System.out.println("The content of arraylist is: " + arl);
System.out.println("The size of an arraylist is: " + arl.size());
</code></pre>

<p>Here is a simple arrayList program. 
ArrayList extends AbstractList and implements List, Cloneable, Serializable. </p>

<p>Here my question is: Is it not necessary to implement all the methods present in above mentioned interface (List, Cloneable, Serializable) by arrayList class (ArrayListDemo).</p>
