面向對象編程語言都提供了內存中對象的複製能力,Java語言提供了對象的淺拷貝和深拷貝。
淺拷貝(Shallow copy):
複製一個對象時,如果它的一個屬性是引用,則複製這個引用,使之指向內存中同一對象。
深拷貝(Deep copy):
但如果爲此屬性創建了一個新對象,讓其引用它,則是深拷貝。
實現深拷貝:使類實現java.io.Serializable接口,把原型對象序列化,然後反序列後得到的對象,其實就是一個新的深拷貝對象。
package com.alex.prototypepattern;
public class DeepCopyBeanTestDrive {
public static void main(String[] args) {
DeepCopyBean originalBean = new DeepCopyBean();
//create a String object in jvm heap
originalBean.setName(new String("alex"));
//create a String object in jvm string pool
//originalBean.setName("alex");
originalBean.setAge(24);
//clone this bean
DeepCopyBean newBean = originalBean.deepCopy();
System.out.println("Primitive field use == tocompare : " + (newBean.getAge() == originalBean.getAge()));
System.out.println("Object field use == to compare : " + (newBean.getName() == originalBean.getName()));
System.out.println("Object field use equal to compare : " + (newBean.getName().equals(originalBean.getName())));
}
}
package com.alex.prototypepattern;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
public class DeepCopyBean implements Serializable{
private String name ;
private int age;
public String getName() {
return name;
}
public int getAge() {
return age;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public DeepCopyBean deepCopy(){
ByteArrayOutputStream buf = new ByteArrayOutputStream();
try {
ObjectOutputStream oos = new ObjectOutputStream(buf);
oos.writeObject(this);
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(buf.toByteArray()));
try {
return (DeepCopyBean)ois.readObject();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}