import java.util.HashSet;
import java.util.Set;

/**
 * This utility class contains some methods for (sets of) integers.
 * 
 * @author Franck van Breugel
 */
public class Test2F 
{
    private Test2F() {}
    
    /**
     * Tests whether the given integer is zero.
     * 
     * @param number an integer.
     * @return true if number is zero, false otherwise.
     */
    public static boolean zero(int number)
    {
	return number == 0;
    }
    
    /**
     * Returns the string "empty" if the given set is empty,
     * and returns the string "nonempty" otherwise.
     * 
     *  @param set a set of integers.
     *  @pre. set != null
     *  @return "empty" if the given set is empty, "nonempty" otherwise.
     */
    public static String empty(Set<Integer> set)
    {
	String result;
	if (set.isEmpty())
	{
	    result = "empty";
	}
	else
	{
	    result = "nonempty";
	}
	return result;
    }
    
    /**
     * Tests whether the given set of integers contains an even integer.
     * For example, for the set { 1, 3, 5, 7 } false is returned and
     * for the set { 1, 2, 3 } true is returned.
     * 
     * @param set a set of integers.
     * @return true if the set contains an even integer, false otherwise.
     */
    public static boolean containsEven(Set<Integer> set)
    {
	boolean containsEven = false;
	for (Integer element : set)
	{
	    containsEven = containsEven || element % 2 == 0;
	}
	return containsEven;
    }
    
    /**
     * Returns the sum of the elements of the symmetric difference of the
     * two given sets.  An element belongs to the symmetric difference if
     * it is contained in one of the two sets, but not in the other.
     * For example, for the sets<br/>
     * { 1, 2, 5, 8 } and {1, 3, 8, 9, 10}<br/>
     * 29 is returned, since 2 + 3 + 5 + 9 + 10 = 29.
     * 
     * @param first a set of integers.
     * @pre. first != null
     * @param second a set of integers.
     * @pre. second != null
     * @return the sum of the elements of the symmetric difference of the
     * two given sets.
     */
    public static int sumOfSymmetricDifference(Set<Integer> first, Set<Integer> second)
    {
	Set<Integer> symmetricDifference = new HashSet<Integer>();
	for (Integer element : first)
	{
	    if (!second.contains(element))
	    {
		symmetricDifference.add(element);
	    }
	}
	for (Integer element : second)
	{
	    if (!first.contains(element))
	    {
		symmetricDifference.add(element);
	    }
	}
	
	int sum = 0;
	for (Integer element : symmetricDifference)
	{
	    sum += element;
	}
	return sum;
    }
}