需求
有一只羊叫tom, 年齡1歲, 顏色是白色, 請編寫程序創(chuàng)建和tom屬性完全相同的10只羊
傳統(tǒng)方式解決克隆羊
直接上代碼吧
public class Sheep {
private String name;
private int age;
private String color;
public Sheep(String name, int age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
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 String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
@Override
public String toString() {
return "Sheep{" +
"name='" + name + '\'' +
", age=" + age +
", color='" + color + '\'' +
'}';
}
}
public class Client {
public static void main(String[] args) {
Sheep sheep = new Sheep("tom", 1, "白色");
Sheep sheep2 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor());
Sheep sheep3 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor());
Sheep sheep4 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor());
Sheep sheep5 = new Sheep(sheep.getName(), sheep.getAge(), sheep.getColor());
System.out.println(sheep);
System.out.println(sheep2);
System.out.println(sheep3);
System.out.println(sheep4);
System.out.println(sheep5);
}
}
輸出結(jié)果:
Sheep{name='tom', age=1, color='白色'}
Sheep{name='tom', age=1, color='白色'}
Sheep{name='tom', age=1, color='白色'}
Sheep{name='tom', age=1, color='白色'}
Sheep{name='tom', age=1, color='白色'}
分析
-
優(yōu)點:
比較好理解, 簡單易操作 - 缺點
- 在創(chuàng)建新的對象時, 總是需要重新獲取原始對象的屬性, 如果創(chuàng)建的對象比較復(fù)雜, 效率較低
- 總是需要重新初始化對象, 而不是動態(tài)的獲得對象運行時的狀態(tài), 不夠靈活
使用原型模式克隆羊
原型模式介紹
- 原型模式指用原型實例指定創(chuàng)建對象的種類, 并且通過拷貝這些原型, 創(chuàng)建新的對象
- 原型模式是一種創(chuàng)建型設(shè)計模式, 允許一個對象創(chuàng)建另外一個可定制的對象, 無需知道創(chuàng)建的細(xì)節(jié)
- 工作原理: 通過將一個對象傳給那個要發(fā)動創(chuàng)建的對象, 這個要發(fā)動創(chuàng)建的對象通過請求原型對象拷貝它們自己來實施創(chuàng)建, 即 對象.clone()
上代碼:
public class Sheep implements Cloneable{
private String name;
private int age;
private String color;
private String address = "蒙古羊";
public Sheep(String name, int age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
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 String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
@Override
public String toString() {
return "Sheep{" +
"name='" + name + '\'' +
", age=" + age +
", color='" + color + '\'' +
", address='" + address + '\'' +
'}';
}
@Override
protected Sheep clone() {
Sheep sheep = null;
try {
sheep = (Sheep) super.clone();
} catch (Exception e) {
e.printStackTrace();
}
return sheep;
}
}
public class Client {
public static void main(String[] args) {
System.out.println("原型模式完成對象的創(chuàng)建");
Sheep sheep = new Sheep("tom", 1, "白色");
Sheep sheep2 = sheep.clone();
Sheep sheep3 = sheep.clone();
Sheep sheep4 = sheep.clone();
Sheep sheep5 = sheep.clone();
System.out.println("sheep2 = " + sheep2);
System.out.println("sheep3 = " + sheep3);
System.out.println("sheep4 = " + sheep4);
System.out.println("sheep5 = " + sheep5);
}
}
淺拷貝與深拷貝
淺拷貝的介紹
- 對于數(shù)據(jù)類型是基本類型的成員變量, 淺拷貝會直接進(jìn)行值傳遞, 將屬性值復(fù)制一份給新的對象
- 對于數(shù)據(jù)類型是引用類型的成員變量, 淺拷貝會進(jìn)行引用傳遞, 只是將該成員變量的引用值復(fù)制一份給新的對象, 在這種情況下在一個對象中修改該成員變量會影響到另一個對象的該成員變量
- 前面的克隆羊就是淺拷貝
假如Sheep增加一個類型為Sheep的成員變量friendprivate Sheep friend, 這個成員變量在拷貝的時候就只會進(jìn)行引用傳遞
深拷貝的介紹
- 復(fù)制對象的所有基本數(shù)據(jù)類型的成員變量
- 為所有引用數(shù)據(jù)類型的成員變量申請存儲空間, 并復(fù)制每個引用數(shù)據(jù)類型成員變量所引用的對象, 直到該對象可達(dá)的所有對象, 也就是說, 要對整個對象進(jìn)行拷貝
- 深拷貝實現(xiàn)方式1: 重寫clone方法實現(xiàn)深拷貝
- 深拷貝實現(xiàn)方式2: 通過對象序列化實現(xiàn)深拷貝(推薦使用)
上代碼:
方式一
首先, 這個DeepCloneableTarget是要拷貝的為引用數(shù)據(jù)類型的成員變量
public class DeepCloneableTarget implements Serializable, Cloneable {
private static final long serialVersionUID = 1L;
private String cloneName;
private String cloneClass;
public DeepCloneableTarget(String cloneName, String cloneClass) {
this.cloneName = cloneName;
this.cloneClass = cloneClass;
}
@Override
protected DeepCloneableTarget clone() throws CloneNotSupportedException {
return (DeepCloneableTarget) super.clone();
}
}
這個DeepProtoType是要拷貝的對象
public class DeepProtoType implements Serializable, Cloneable {
private String name;
private DeepCloneableTarget deepCloneableTarget;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public DeepCloneableTarget getDeepCloneableTarget() {
return deepCloneableTarget;
}
public void setDeepCloneableTarget(DeepCloneableTarget deepCloneableTarget) {
this.deepCloneableTarget = deepCloneableTarget;
}
public DeepProtoType() {
}
public DeepProtoType(String name, DeepCloneableTarget deepCloneableTarget) {
this.name = name;
this.deepCloneableTarget = deepCloneableTarget;
}
// 深拷貝, 方式一: 使用clone方法
@Override
protected DeepProtoType clone() throws CloneNotSupportedException {
DeepProtoType deepProtoType = null;
deepProtoType = (DeepProtoType) super.clone();
deepProtoType.setDeepCloneableTarget(deepProtoType.getDeepCloneableTarget().clone());
return deepProtoType;
}
}
public class Client {
public static void main(String[] args) throws CloneNotSupportedException {
DeepProtoType p = new DeepProtoType();
p.setName("宋江");
p.setDeepCloneableTarget(new DeepCloneableTarget("大牛", "小牛"));
// 方式一完成深拷貝
DeepProtoType p2 = p.clone();
DeepProtoType p3 = p.clone();
DeepProtoType p4 = p.clone();
DeepProtoType p5 = p.clone();
System.out.println("p.name = " + p.getName() + ", p.getDeepCloneableTarget().hashCode() = "+p.getDeepCloneableTarget().hashCode());
System.out.println("p2.name = " + p2.getName() + ", p2.getDeepCloneableTarget().hashCode() = "+p2.getDeepCloneableTarget().hashCode());
System.out.println("p3.name = " + p3.getName() + ", p3.getDeepCloneableTarget().hashCode() = "+p3.getDeepCloneableTarget().hashCode());
System.out.println("p4.name = " + p4.getName() + ", p4.getDeepCloneableTarget().hashCode() = "+p4.getDeepCloneableTarget().hashCode());
System.out.println("p5.name = " + p5.getName() + ", p5.getDeepCloneableTarget().hashCode() = "+p5.getDeepCloneableTarget().hashCode());
}
}
輸出結(jié)果:
p.name = 宋江, p.getDeepCloneableTarget().hashCode() = 1625635731
p2.name = 宋江, p2.getDeepCloneableTarget().hashCode() = 1580066828
p3.name = 宋江, p3.getDeepCloneableTarget().hashCode() = 491044090
p4.name = 宋江, p4.getDeepCloneableTarget().hashCode() = 644117698
p5.name = 宋江, p5.getDeepCloneableTarget().hashCode() = 1872034366
方式二
public class DeepProtoType implements Serializable, Cloneable {
private String name;
private DeepCloneableTarget deepCloneableTarget;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public DeepCloneableTarget getDeepCloneableTarget() {
return deepCloneableTarget;
}
public void setDeepCloneableTarget(DeepCloneableTarget deepCloneableTarget) {
this.deepCloneableTarget = deepCloneableTarget;
}
public DeepProtoType() {
}
public DeepProtoType(String name, DeepCloneableTarget deepCloneableTarget) {
this.name = name;
this.deepCloneableTarget = deepCloneableTarget;
}
// 深拷貝, 方式二: 通過對象的序列化(推薦)
public DeepProtoType deepClone() {
ByteArrayOutputStream bos = null;
ObjectOutputStream oos = null;
ByteArrayInputStream bis = null;
ObjectInputStream ois = null;
try {
// 序列化
bos = new ByteArrayOutputStream();
oos = new ObjectOutputStream(bos);
oos.writeObject(this);
// 反序列化
bis = new ByteArrayInputStream(bos.toByteArray());
ois = new ObjectInputStream(bis);
DeepProtoType copy = (DeepProtoType) ois.readObject();
return copy;
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
try {
bos.close();
oos.close();
bis.close();
ois.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public class Client {
public static void main(String[] args) throws CloneNotSupportedException {
DeepProtoType p = new DeepProtoType();
p.setName("宋江");
p.setDeepCloneableTarget(new DeepCloneableTarget("大牛", "小牛"));
// 方式二完成深拷貝
DeepProtoType p2 = p.deepClone();
DeepProtoType p3 = p.deepClone();
DeepProtoType p4 = p.deepClone();
DeepProtoType p5 = p.deepClone();
System.out.println("p.name = " + p.getName() + ", p.getDeepCloneableTarget().hashCode() = "+p.getDeepCloneableTarget().hashCode());
System.out.println("p2.name = " + p2.getName() + ", p2.getDeepCloneableTarget().hashCode() = "+p2.getDeepCloneableTarget().hashCode());
System.out.println("p3.name = " + p3.getName() + ", p3.getDeepCloneableTarget().hashCode() = "+p3.getDeepCloneableTarget().hashCode());
System.out.println("p4.name = " + p4.getName() + ", p4.getDeepCloneableTarget().hashCode() = "+p4.getDeepCloneableTarget().hashCode());
System.out.println("p5.name = " + p5.getName() + ", p5.getDeepCloneableTarget().hashCode() = "+p5.getDeepCloneableTarget().hashCode());
}
}
輸出結(jié)果:
p.name = 宋江, p.getDeepCloneableTarget().hashCode() = 723074861
p2.name = 宋江, p2.getDeepCloneableTarget().hashCode() = 2093176254
p3.name = 宋江, p3.getDeepCloneableTarget().hashCode() = 1854731462
p4.name = 宋江, p4.getDeepCloneableTarget().hashCode() = 317574433
p5.name = 宋江, p5.getDeepCloneableTarget().hashCode() = 885284298
總結(jié)
- 創(chuàng)建新的對象比較復(fù)雜時, 可以使用原型模式簡化對象的創(chuàng)建, 也能提高效率
- 不用重新初始化對象, 而是動態(tài)的獲得對象運行時的狀態(tài)
- 如果原始對象增加或減少屬性, 其克隆對象也會發(fā)生相應(yīng)的變化, 而無需修改代碼
- 實現(xiàn)深克隆的時候可能需要比較復(fù)雜的代碼
- 缺點: 需要為每一個類配備一個克隆方法, 對全新的類來說不難, 但是對已有類進(jìn)行改造時, 需要修改其源代碼, 違背了ocp原則, 這點需要注意
小結(jié)
代碼地址：
https://github.com/mundane799699/DesignPattern/tree/master/Prototype/src/com/mundane/prototype
參考:
