Class CallHandler

java/Chapter 8/Question8_2/CallHandler.java:11–113

 * and all calls are funneled first through it. 
 */
public class CallHandler {
	private static CallHandler instance;
	
	/* We have 3 levels of employees: respondents, managers, directors. */
    private final int LEVELS = 3; 
    
    /* Initialize with 10 respondents, 4 managers, and 2 directors. */
    private final int NUM_RESPONDENTS = 10;
    private final int NUM_MANAGERS = 4;
    private final int NUM_DIRECTORS = 2;

    /* List of employees, by level.
     * employeeLevels[0] = respondents
     * employeeLevels[1] = managers
     * employeeLevels[2] = directors
     */
    List<List<Employee>> employeeLevels;

	/* queues for each call�s rank */
    List<List<Call>> callQueues; 

    protected CallHandler() {
    	employeeLevels = new ArrayList<List<Employee>>(LEVELS);
    	callQueues = new ArrayList<List<Call>>(LEVELS); 
    	
        // Create respondents.
        ArrayList<Employee> respondents = new ArrayList<Employee>(NUM_RESPONDENTS);
        for (int k = 0; k < NUM_RESPONDENTS - 1; k++) {
            respondents.add(new Respondent());
        }
        employeeLevels.add(respondents);

        // Create managers.
        ArrayList<Employee> managers = new ArrayList<Employee>(NUM_MANAGERS);
        managers.add(new Manager());
        employeeLevels.add(managers);

        // Create directors.
        ArrayList<Employee> directors = new ArrayList<Employee>(NUM_DIRECTORS);
        directors.add(new Director());
        employeeLevels.add(directors);
    }
    
    /* Get instance of singleton class. */
    public static CallHandler getInstance() {
    	if (instance == null) {
    		instance = new CallHandler();
    	}
    	return instance;
    }
    
    /* Gets the first available employee who can handle this call. */
    public Employee getHandlerForCall(Call call) {
        for (int level = call.getRank().getValue(); level < LEVELS - 1; level++) {
            List<Employee> employeeLevel = employeeLevels.get(level);
            for (Employee emp : employeeLevel) {
                if (emp.isFree()) {
                    return emp;