Java示例队列实现

import java.util.LinkedList;



class GenQueue<E> {

   private LinkedList<E> list = new LinkedList<E>();

   public void enqueue(E item) {

      list.addLast(item);

   }

   public E dequeue() {

      return list.poll();

   }

   public boolean hasItems() {

      return !list.isEmpty();

   }

   public int size() {

      return list.size();

   }

   public void addItems(GenQueue<? extends E> q) {

      while (q.hasItems()) list.addLast(q.dequeue());

   }

}

public class GenQueueTest {

   public static void main(String[] args) {

      GenQueue<Employee> empList;

      empList = new GenQueue<Employee>();

      GenQueue<HourlyEmployee> hList;



      hList = new GenQueue<HourlyEmployee>();

      hList.enqueue(new HourlyEmployee("T", "D"));

      hList.enqueue(new HourlyEmployee("G", "B"));

      hList.enqueue(new HourlyEmployee("F", "S"));

      empList.addItems(hList);

      System.out.println("The employees' names are:");



      while (empList.hasItems()) {

         Employee emp = empList.dequeue();

         System.out.println(emp.firstName + " " + emp.lastName);

      }

   }

}

class Employee {

   public String lastName;

   public String firstName;

   public Employee() {

   }

   public Employee(String last, String first) {

      this.lastName = last;

      this.firstName = first;

   }

   public String toString() {

      return firstName + " " + lastName;

   }

}

class HourlyEmployee extends Employee {

   public double hourlyRate;

   public HourlyEmployee(String last, String first) {

      super(last, first);

   }

}