import java.util.*;

/**
 * BasicArrayList.java<br>
 * Illustrates the implementation of several of the ArrayList methods.
 * <p>
 * Created: Wed Feb 19 11:24:05 2003
 *
 * @author <a href="mailto:shapiro@cse.buffalo.edu">Stuart C. Shapiro</a><br>
 * Documentation from <a
 * href="http://java.sun.com/j2se/1.4/docs/api/java/util/ArrayList.html">Java API</a>
 */

public class BasicArrayList extends AbstractList {
    private Object[] array;
    private int capacity;
    private int currentSize;

    /**
     * Constructs an empty list with the specified initial capacity.
     *
     * @param initialCapacity the initial capacity of the list.
     * @exception IllegalArgumentException
     * if the specified initial capacity is negative
     */
    public BasicArrayList (int initialCapacity) throws IllegalArgumentException {
	super();
	if (initialCapacity < 0) {
	    throw new IllegalArgumentException();
	}	
	capacity = initialCapacity;
	array = new Object[capacity];
	currentSize = 0;
    }

    /**
     * Constructs an empty list with an initial capacity of ten.
     *
     */
    public BasicArrayList (){
	this(10);
    }

    /**
     * Returns the element at the specified position in this list.
     *
     * @param index  index of element to return.
     * @return the element at the specified position in this list.
     * @exception IndexOutOfBoundsException if index out of range
     * (index < 0 || index >= size()).
     */
    public Object get(int index) throws IndexOutOfBoundsException {
	if (index < 0 || index >= currentSize) {
	    throw new IndexOutOfBoundsException();
	}	
	return array[index];
    }

    /**
     * Returns the number of elements in this list.
     *
     * @return the number of elements in this list.
     */
    public int size() {
	return currentSize;
    }

    /**
     * Appends the specified element to the end of this list.
     *
     * @param o element to be appended to this list.
     * @return true (as per the general contract of Collection.add).
     */
    public boolean add(Object o) {
	if (currentSize == capacity) {
	    Object[] oldarray = array;
	    capacity *= 2;
	    array = new Object[capacity];
	    for (int i = 0; i < currentSize; i++) {
		array[i] = oldarray[i];
	    } // end of for (int i = 0; i < currentSize-1; i++)
	} // end of if (currentSize == capacity)
	array[currentSize++] = o;
	return true;
    }

    /**
     * Removes the element at the specified position in this
     * list. Shifts any subsequent elements to the left (subtracts one
     * from their indices).
     *
     * @param index the index of the element to removed.
     * @return the element that was removed from the list.
     * @exception IndexOutOfBoundsException if index out of range
     * (index < 0 || index >= size()).
     */
    public Object remove(int index) throws IndexOutOfBoundsException {
	if (index < 0 || index >= currentSize) {
	    throw new IndexOutOfBoundsException();
	}	
	Object result = array[index];
	for (int i = index; i < currentSize-1; i++) {
	    array[i] = array[i+1];
	} // end of for (int i = index; i < currentSize-1; i++)
	currentSize--;
	return result;
    }

    /**
     * Returns a string representation of this list.
     *
     * @return a string representation of this list.
     */
    public String toString() {
	String result = "[";
	for (int i = 0; i < currentSize-1; i++)
	    result += array[i] + ", ";
	if (currentSize > 0) {
	    result += array[currentSize-1];
	}
	return result + "]";
    }
	
    
}// BasicArrayList