what i doing wrong??

import java.util.ArrayDeque;
import java.util.Queue;

//This is a Call Center application. 
//There is a group of Customer Support Representatives 
//that assist Customers. 
//When representatives become available they enter the queue. 
//The acceptCustomer method gets called when a new customer phones in.
// I've left 3 things for you todo in the comments below.
//All other code is only for your reference, no need to change it.
public class CallCenter {
  private Queue<CustomerSupportRep> mSupportReps;

  public CallCenter(Queue<CustomerSupportRep> queue) {
    mSupportReps = queue;
  }

  public void acceptCustomer(Customer customer) {

      CustomerSupportRep csr; 

     while(mSupportReps.size() < 0)
            {
                playHoldMusic();

            }

    if (mSupportReps.size() > -1)
       {
       csr = new CustomerSupportRep("zang");

        csr.assist(customer);
        mSupportReps.add("zang");

     }






  }

  public void playHoldMusic() {
    System.out.println("Smooooooth Operator.....");
  }

}

import java.util.List;
import java.util.ArrayList;

public class CustomerSupportRep {
  private String mName;
  private List<Customer> mAssistedCustomers;

  public CustomerSupportRep(String name) {
    mName = name;
    mAssistedCustomers = new ArrayList<Customer>();
  }

  public void assist(Customer customer) {
    System.out.printf("Hello %s, my name is %s, how can I assist you.%n",
                      customer.getName(),
                      mName);
    System.out.println("...");
    System.out.println("Is there anything else I can help you with?");
    mAssistedCustomers.add(customer);
  }

  public List<Customer> getAssistedCustomers() {
    return mAssistedCustomers;
  }

}

public class Customer {
  private String mName;

  public Customer(String name) {
    mName = name;
  }

  public String getName() {
    return mName;
  }

}