APCS/05 Collections _ Generics/01 TJArrayList/TJArrayList.java

// Name: B6-24
// Date: 12/4/19

/**
 * Implements the cheat sheet's List interface.  Implements generics.
 * The backing array is an array of (E[]) new Object[10];
 * @override toString()
 */ 
public class TJArrayList<E>
{
   private int size;							//stores the number of objects
   private E[] myArray;
   public TJArrayList()                //default constructor makes 10 cells
   {
      myArray = (E[]) new Object[10];
      size = 0;
   }
   public int size()
   {
      return size;   
   }
 	/* appends obj to end of list; increases size;
      must be an O(1) operation when size < array.length, 
         and O(n) when it doubles the length of the array.
	  @return true  */
   public boolean add(E obj)
   {
      if (size < myArray.length) {
         myArray[size] = obj;   
      } else {
         E[] temp = (E[]) new Object[myArray.length * 2];
         for (int i = 0; i < size; i++)
            temp[i] = myArray[i];
         temp[size] = obj;
         myArray = temp;
      }
      size++;
      return true;
   }
   /* inserts obj at position index.  increments size. 
		*/
   public void add(int index, E obj) throws IndexOutOfBoundsException  //this the way the real ArrayList is coded
   {
      if(index > size || index < 0)
         throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
      if (size < myArray.length) {
         System.arraycopy(myArray, index, myArray, index + 1, size - index);
         myArray[index] = obj;
         size++;
      } else {
         E[] temp = (E[]) new Object[myArray.length * 2];
         for (int i = 0; i < size; i++)
            temp[i] = myArray[i];
         myArray = temp;
         add(index, obj);
      }
   }

   /* return obj at position index.  
		*/
   public E get(int index) throws IndexOutOfBoundsException
   {
      if(index >= size || index < 0)
         throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
      return myArray[index];
   
   }
   /**
    * Replaces obj at position index. 
    * @return the object is being replaced.
    */  
   public E set(int index, E obj) throws IndexOutOfBoundsException  
   { 
      if(index >= size || index < 0)
         throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
      E temp = myArray[index];
      myArray[index] = obj;
      return temp;
   }
 /*  removes the node from position index. shifts elements 
     to the left.   Decrements size.
	  @return the object at position index.
	 */
   public E remove(int index) throws IndexOutOfBoundsException  
   {
      if(index >= size || index < 0)
         throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
      
      E temp = myArray[index];
      System.arraycopy(myArray, index + 1, myArray, index, size - index - 1);
      myArray[size--] = null;
      return temp;
   }
	   /*
		   This method compares objects.
         Must use .equals(), not ==
     	*/
   public boolean contains(E obj)
   {
      for (int i = 0; i < size; i++) 
         if (myArray[i].equals(obj))
            return true;
      return false;
   }
	 /*returns a String of E objects in the array with 
       square brackets and commas.
     	*/
   public String toString()
   {
      String string = "[";
      for (int i = 0; i < size; i++) {
         string += myArray[i].toString();
         if (i != size - 1) {
            string += ", ";
         }
      }
      
      return string + "]"; 
   }
}