原型模式(詳解)

一、概念

用一個已經創建的實例作爲原型，通過複製該原型對象來創建一個和原型相同或相似的新對象。在這裏，原型實例指定了要創建的對象的種類。用這種方式創建對象非常高效，根本無須知道對象創建的細節。

 

二、深拷貝和淺拷貝

淺拷貝：只是新建了一個句柄，句柄指向的內存地址不變

深拷貝：新建句柄，指向的內存地址發生了變化

 

三、實現

１．淺拷貝

package com.moshi;


public class Test{
	public static void main(String[] args) throws CloneNotSupportedException {
		User user1 = new User("aa", 12,new Book("一本書"));
		User user2 = (User) user1.clone();
		user2.setName("bb");
		user2.getBook().setBookName("二本書");
		System.out.println(user1.getName());
		System.out.println(user1.getBook().getBookName());
		System.out.println(user1.getBook().hashCode()+"======="+user2.getBook().hashCode());
	}
}

class User implements Cloneable{
	
	private String name;
	
	private int age;
	
	private Book book;
	
	public User(String name, int age,Book book) {
		super();
		this.name = name;
		this.age = age;
		this.book = book;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	
	public Book getBook() {
		return book;
	}

	public void setBook(Book book) {
		this.book = book;
	}

	@Override
	protected Object clone() throws CloneNotSupportedException {
		return super.clone();
	}
}

class Book{
	
	private String bookName;

	public Book(String bookName) {
		super();
		this.bookName = bookName;
	}

	public String getBookName() {
		return bookName;
	}

	public void setBookName(String bookName) {
		this.bookName = bookName;
	}
	
}

 

輸出結果:aa
二本書
366712642=======366712642

可以發現，兩個對象所依賴的對象的hashcode是同一個對象，引用的內存地址還是同一個。

 

２．深拷貝

package com.moshi;


public class Test{
	public static void main(String[] args) throws CloneNotSupportedException {
		User user1 = new User("aa", 12,new Book("一本書"));
		User user2 = (User) user1.clone();
		user2.setName("bb");
		user2.getBook().setBookName("二本書");
		System.out.println(user1.getName());
		System.out.println(user1.getBook().getBookName());
		System.out.println(user1.getBook().hashCode()+"======="+user2.getBook().hashCode());
	}
}

class User implements Cloneable{
	
	private String name;
	
	private int age;
	
	private Book book;
	
	public User(String name, int age,Book book) {
		super();
		this.name = name;
		this.age = age;
		this.book = book;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	
	public Book getBook() {
		return book;
	}

	public void setBook(Book book) {
		this.book = book;
	}

	@Override
	protected Object clone() throws CloneNotSupportedException {
		User  user = (User) super.clone();
		user.book = (Book) user.getBook().clone();
		return user;
	}
}

class Book implements Cloneable{
	
	private String bookName;

	public Book(String bookName) {
		super();
		this.bookName = bookName;
	}

	public String getBookName() {
		return bookName;
	}

	public void setBookName(String bookName) {
		this.bookName = bookName;
	}
	@Override
	protected Object clone() throws CloneNotSupportedException {
		return super.clone();
	}

}

輸出結果:

aa
一本書
366712642=======1829164700

可以發現，重寫clone方法後，兩個對象所依賴的對象的hashCode不一致了。則表示引用的內存地址不一致。

 

五、原型模式

原型模式便是通過clone方法來創建相同或者相似的類。以此可以提高程序性能。