import java.util.Iterator;
import java.util.List;
import java.util.ArrayList;
import java.util.Set;

/**
 * Holds a voter's ballot.
 * @author Scot Drysdale
 */
public class Ballot {
  private List<String> ballot;  // holds the voter's choices (in order given)
  
  /**
   * Constructs an empty ballot.
   */
  public Ballot() {
    ballot = new ArrayList<String>();
  }
  
  /**
   * Finds and returns the top choice among candidates.
   * @param candidates the current set of candidates
   * @return name of top choice in candidates, or null if none exists.
   */
  public String getTopChoice(Set<String> candidates) {
    Iterator<String> iter = ballot.iterator();
    while (iter.hasNext()) {
      String candidate = iter.next();
      if (candidates.contains(candidate))
        return candidate;
    }
    return null;  // none of the candidates on ballot were in candidates
  }
  
  /**
   * Returns the first candidate on the ballot
   * @return the first candidate on the ballot, or null if none exists
   */
  public String getFirst() {
    if (ballot.size() > 0)
      return ballot.get(0);
    else
      return null;
  }
  
  /**
   * Adds candidate to this ballot.
   * @param candidate the candidate to add
   */
  public void addCandidate(String candidate) {
    ballot.add(candidate);
  }
  
  /**
   * Returns a string with the candidates
   */
  public String toString() {
    return ballot.toString();
  }
}