/**
 * 
 */
package student_classes;

/**
 * <P>Simulates the old-fashioned "vector" class, which behaved a lot like an array
 * that could shrink and grow.<br>
 * Note: one might think of this class definition as an introduction to the <code>ArrayList</code>
 * data-type, which will be introduced within the next week or so.
 * </P>
 * @author Tom R
 *
 */
public class Vector {
	private Object[] vector; // note this data type ...
	private static final int DEFAULT_SIZE=16; // initial size
	private static final int QUANTA=8; // how many buckets to add ...
	/* ask yourself: why is this next instance variables necessary?
	 * How will it be used?
	 */
	private int effective_index = 0;

	
	// ctor(s):
	public Vector() {
		// default ctor, makes an array of the default size.
		this.vector = new Object[ DEFAULT_SIZE ];
	}
	// public interface:
	public void add( Object element ) {
		if( this.effective_index < this.vector.length ) {
			this.vector[ this.effective_index++ ] = element;
			return;
		}
		this.growVector();
		this.vector[ this.effective_index++ ] = element;

	}
	
	private void growVector() {
		Object[] replacementVector = new Object[ this.vector.length + QUANTA ];
		// copy the contents of the existing vector into the replacement
		// vector, 
		for( int index = 0; index < this.vector.length; index++ ) 
			replacementVector[ index ] = this.vector[ index ];
		this.vector = replacementVector;
	}
	
	
	// overrides ...
	public String toString() {
		StringBuilder str = new StringBuilder();
		str.append("[ ");
		/* why can't we just print from 0 through the effective_index? */
		for( int index = 0; index < this.effective_index; index++ ) 
			str.append( this.vector[ index ].toString() +", " );
		
		str.append("]");
		return str.toString();
	}

}