设计模式 -- 原型模式

介绍

• 原型模式（Prototype Pattern）是用于创建重复的对象，同时又能保证性能

• 核心

  1. 实现Cloneable接口，该接口的作用是通知虚拟机可以安全使用实现该接口的类的clone()方法
  
  2. 重写clone()方法
  

• 注意：在java中，只有实现了该接口才能被拷贝，否则抛出java.lang.CloneNotSupportedException异常

使用场景

• 资源优化

• 类初始化需要消化非常多的资源，这个资源包括数据、硬件资源等

• 通过 new 产生一个对象需要非常繁琐的数据准备或访问权

• 一个对象需要提供给其他对象访问，而且各个调用者可能都需要修改其值时

案例

• 创建Student类，实现Cloneable接口，重写clone()方法

  
  public class Student implements Cloneable{
  
      private String name;
      private Integer age;
      private School school;
  
      private Student student = null;
  
      public Student(String name, Integer age, School school) {
          this.name = name;
          this.age = age;
          this.school = school;
      }
  
      @Override
      protected Object clone() throws CloneNotSupportedException {
          // 对基本数据类型和string的拷贝
          student = (Student) super.clone();
          // 对引用类型进行拷贝（深拷贝）
          student.school = (School) this.school.clone();
          return student;
      }
  
      public Integer getAge() {
          return age;
      }
  
      public void setAge(Integer age) {
          this.age = age;
      }
  
      public School getSchool() {
          return school;
      }
  
      public void setSchool(School school) {
          this.school = school;
      }
  
      @Override
      public String toString() {
          return "Student{" +
                  "name='" + name + '\'' +
                  ", age=" + age +
                  ", school=" + school +
                  '}';
      }
  }
  

• 创建School类，实现Cloneable接口，重写clone()方法

  
  public class School implements Cloneable{
  
      private String addr;
      private String classroom;
  
      public School(String addr,String classroom){
          this.addr = addr;
          this.classroom = classroom;
      }
  
      @Override
      protected Object clone() throws CloneNotSupportedException {
          return super.clone();
      }
  
      @Override
      public String toString() {
          return "School{" +
                  "addr='" + addr + '\'' +
                  ", classroom='" + classroom + '\'' +
                  '}';
      }
  }
  

• 编写测试类

  public class Test {
  
      public static void main(String[] args) throws CloneNotSupportedException {
  
          School school = new School("二中","初一三班");
          Student mike = new Student("mik1",15,school);
  
          System.out.println(mike.toString());
          System.out.println("Mike升到了高中");
  
          Student mike2 = (Student) mike.clone();
          School school2 = new School("一中","高三六班");
          mike2.setSchool(school2);
          mike2.setAge(20);
  
          System.out.println(mike2.toString());
      }
  
  }
  

  运行结果