[Data Structure] Set Implementation

public class Set {
      private T arrayElement[];
      int size =0;
      public Set(){
            this.arrayElement = null;
  	}
      public Set(T[] element){
        	arrayElement = element;// array can be assigned
        	size = arrayElement.length;
  	}
  	/**
  	 *add element to set. A check is made to identify whether element is present or not.
  	 *If not the element can be inserted.
  	 * @param element
  	 */
      public void addElement(T element){
            if(!contains(element)){
                    if(size == arrayElement.length){
              	       incrementArray();
        	          }
        	          arrayElement[size++] = element;
        	  }
       }
     
  	/**
  	 * to check is element is present or not.
  	 * @param elem
  	 * @return boolean
  	 */
O(n)
      public boolean contains(T elem){
 
            if (elem == null) {
        	    for (int i = 0; i < size; i++)
                  if (arrayElement[i]==null)
              	    return true;
        	} else {
        	    for (int i = 0; i < size; i++)
                  if (elem.equals(arrayElement[i]))
              	    return true;
        	}
            return false;
  	   
  	}
     	/**
  	 * this function is used to increment the size of an array
  	 *
  	 */
      private void incrementArray(){
        	T[] temparray = arrayElement;
            int tempsize=size+5;
        	 arrayElement =(T[]) new Object[tempsize];
        	 System.arraycopy(temparray, 0, arrayElement, 0, size);
        	 
  	}
public static void arraycopy(Object src,
                             int srcPos,
                             Object dest,
                             int destPos,
                             int length)
http://www.java-samples.com/showtutorial.php?tutorialid=641 
The difference is that Arrays.copyOf does not only copy elements, it also creates a new array.System.arrayCopy copies into an existing array.
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 2, 3, 4, 5, 0, 0, 0, 0]
[1, 2, 3, 4, 5, 0, 0, 0, 0, 0]
[1, 2, 3]
http://www.programcreek.com/2015/03/system-arraycopy-vs-arrays-copyof-in-java/
  	/**
  	 * return the size of set.
  	 * @return int
  	 */
      public int size(){
            if(arrayElement != null){
                  return arrayElement.length;
        	}else
                  return 0;
  	}
     
      public void clear(){
        	arrayElement = null;
  	}
     
      public String toString(){
            if(arrayElement == null  || arrayElement.length ==0 ){
                  return“[EMPTY]”;
        	}else{
              	String toStr=”[“;
                  for(int i=0;i