使用通配符类型参数的通用队列类

import java.util.LinkedList;


public class Main {

  public static void main(String[] args) {
  /*
  来 自*
   n  o  w  j  a  v  a . c o m
  */

    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);


    while (empList.hasItems()) {

      Employee emp = empList.dequeue();/**来自 nowjava.com**/

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

    }

  }

}


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());

  }

}


class Employee {

  public String lastName;

  public String firstName;


  public Employee() {

  }


  public Employee(String last, String first) {

    this.lastName = last;

    this.firstName = first;

  }