/**
@author  Scott Marshall
@author  University of Glasgow, MSc IT Project 2001
@author  Building an OnLine Course in Computing Fundamentals

Multiple Choice Questions

*/

package ukacgla_HTMLMulti;

import ukacgla_HTMLMulti.*;
import java.util.*;

/**
This class constructs an object whose sole purpose is to randomly
re arrange the elements of a vector, without altering the elements themselves.
*/
public class TestRandomiser {

	private  Random rand;		//random number generator
	private int numQuestions;	//size of  vector to be returned.

	public TestRandomiser(int n) {
		rand = new Random();
		numQuestions = n;	
	}



	//------------------ RANDOMISE METHODS ------------------------------------------

	
	/**
	Generates a random number between 0(inclusive) and n(exclusive)
	If n is zero, will throw new IllegalArgumentException("n must be positive");
	*/
	private int genRandom(int n)	{
		Random rand = new Random();
		int r = rand.nextInt(n);
		return r;
	
	}

	
	/**
	Copies the elements of a vector into a new Vector, then returns the vector.
	The returned Vector has the same elements, but in a different order
	*/
	protected Vector randomise(Vector original){	
		Vector copy = new Vector();
		while (copy.size() < numQuestions )	{  
			int source = genRandom(original.size());
			copy.add(original.get(source));
			original.removeElementAt(source);
			original.trimToSize();
		}
		
		return copy;
	 
	}//ends randomise

}