原型模式簡介
- 模式屬于創(chuàng)建型模式隶债，它提供了一種創(chuàng)建對象的最佳方式。
- 用于創(chuàng)建重復的對象乒裆，同時又能保證性能。
- 這種模式是實現(xiàn)了一個原型接口推励，該接口用于創(chuàng)建當前對象的克隆鹤耍。當直接創(chuàng)建對象的代價比較大時肉迫，則采用這種模式。
- 例如稿黄，一個對象需要在一個高代價的數(shù)據(jù)庫操作之后被創(chuàng)建喊衫。我們可以緩存該對象，在下一個請求時返回它的克隆杆怕，在需要的時候更新數(shù)據(jù)庫族购，以此來減少數(shù)據(jù)庫調用。
淺克隆
類Book實現(xiàn)Cloneable接口并重寫clone方法
public class Book implements Cloneable {
private String name;//書名
private Date publishDate;//發(fā)布日期
public Book() {
}
public Book(String name, Date publishDate) {
this.name = name;
this.publishDate = publishDate;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getPublishDate() {
return publishDate;
}
public void setPublishDate(Date publishDate) {
this.publishDate = publishDate;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
@Override
public String toString() {
return "Book{" +
"name='" + name + '\'' +
", publishDate=" + publishDate +
'}';
}
}
測試類
public class Test {
public static void main(String[] args) throws CloneNotSupportedException {
String name = "Java 設計模式";
Date publishDate = new Date();
Book book = new Book(name, publishDate);
//克隆出對象
Book clone = (Book) book.clone();
System.out.println(book);
System.out.println(book.hashCode());
System.out.println(clone);
System.out.println(clone.hashCode());
System.out.println("==================");
publishDate.setTime(publishDate.getTime() + 2000);//修改時間
System.out.println(book);
System.out.println(book.hashCode());
System.out.println(clone);
System.out.println(clone.hashCode());
/**
* 測試結果：修改了時間陵珍，源對象和克隆的對象的時間寝杖，都發(fā)生了改變
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
* 2093631819
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
* 2074407503
* ==================
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
* 2093631819
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
* 2074407503
*/
}
}
測試結果
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
2093631819
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
2074407503
==================
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
2093631819
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
2074407503
深克隆
類Book實現(xiàn)Cloneable接口并重寫clone方法
public class Book implements Cloneable {
private String name;//書名
private Date publishDate;//發(fā)布日期
public Book() {
}
public Book(String name, Date publishDate) {
this.name = name;
this.publishDate = publishDate;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getPublishDate() {
return publishDate;
}
public void setPublishDate(Date publishDate) {
this.publishDate = publishDate;
}
@Override
protected Object clone() throws CloneNotSupportedException {
Object obj = super.clone();
Book book = (Book) obj;
//將源對象的屬性也進行克隆，即深克隆
book.publishDate = (Date) book.publishDate.clone();
return obj;
}
@Override
public String toString() {
return "Book{" +
"name='" + name + '\'' +
", publishDate=" + publishDate +
'}';
}
}
測試類
public class Test {
public static void main(String[] args) throws CloneNotSupportedException {
String name = "Java 設計模式";
Date publishDate = new Date();
Book book = new Book(name, publishDate);
//克隆出對象
Book clone = (Book) book.clone();
System.out.println(book);
System.out.println(book.hashCode());
System.out.println(clone);
System.out.println(clone.hashCode());
System.out.println("==================");
publishDate.setTime(publishDate.getTime() + 2000);
System.out.println(book);
System.out.println(book.hashCode());
System.out.println(clone);
System.out.println(clone.hashCode());
/**
* 測試結果：修改了時間互纯，源對象的時間瑟幕，發(fā)生了改變，但克隆的對象的時間沒有改變
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
* 2093631819
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
* 2074407503
* ==================
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:49 CST 2021}
* 2093631819
* Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
* 2074407503
*/
}
}
測試結果
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
2093631819
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
2074407503
==================
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:49 CST 2021}
2093631819
Book{name='Java 設計模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
2074407503
