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在正式的進入主題之前，我們先來懂得下深拷貝和前拷貝的概念：
淺拷貝：
會創立一個新對象，這個對象有著原始對象屬性值的一份准確拷貝，假如屬性是根本類型，拷貝的是根本類型的值；假如屬性是內存地址，拷貝的就是內存地址，是以假如一個對象轉變了這個地址就會影響到另外一個對象；
深拷貝：
不只要復制對象的一切非援用成員變量值，還要為援用類型的成員變量創立新的實例，而且初始化為情勢參數實例值；
懂得完概念以後，我們來測試下通俗的對象賦值操作屬於深拷貝照樣淺拷貝：
測試代碼：
public class DepthCopy {
public static void main(String[] args) {
Copy first = new Copy("hzw", 24);
Copy second = first;
second.name = "shanxi";
System.out.println(first.name);//輸入shanxi
}
}
class Copy
{
public String name;
public int age;
public Copy(String name,int age) {
this.name = name;
this.age = age;
}
}
可以發明，在second將name屬性值修正為shanxi以後，first的name屬性值也釀成了shanxi，這點便可以看出通俗的對象賦值屬於淺拷貝；
明確了對象之間賦值是淺拷貝以後，接上去我們來看看克隆究竟是深拷貝照樣淺拷貝，測試代碼是讓下面的Copy對象完成Cloneable接口外面的clone辦法：
public class DepthCopy {
public static void main(String[] args) {
Copy first = new Copy("hzw", 24);
Copy second = null;
try {
second = (Copy) first.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
second.name = "shanxi";
System.out.println(first.name);//輸入: hzw
System.out.println(first);//輸入: com.hzw.day33.Copy@7f39ebdb
System.out.println(second);//輸入: com.hzw.day33.Copy@33abb81e
}
}
class Copy implements Cloneable
{
public String name;
public int age;
public Copy(String name,int age) {
this.name = name;
this.age = age;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
可以看出本來創立出的對象first和克隆創立出的對象second是兩個實例，是以關於second中name屬性的修正其實不會影響first中的name屬性；然則，我們其實不能純真的以為克隆就是深拷貝的，好比上面這個例子：
public class DepthCopy {
public static void main(String[] args) {
Student student = new Student(95);
Copy first = new Copy("hzw", 24,student);
Copy second = null;
try {
second = (Copy) first.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
second.name = "shanxi";
second.student.score = 60;
System.out.println(first == second);//false
System.out.println(first.student == second.student);//true
System.out.println(first.student.score);//60
}
}
class Copy implements Cloneable
{
public String name;
public int age;
public Student student;
public Copy(String name,int age,Student student) {
this.name = name;
this.age = age;
this.student = student;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
class Student
{
public int score;
public Student(int score) {
this.score = score;
}
}
看到沒有呢？我們經由過程克隆的方法創立了second，很顯著發明first和second是兩個實例，由於first == second輸入為false,然則first和second外面的student對象倒是一樣的，經由過程second修正了student的score值以後，first外面student的score也產生了轉變，這也就是說first和second外面的student是雷同的，這也就解釋了克隆是淺拷貝的，我們要想完成克隆的深拷貝，必需讓Copy對象外面的Student對象也要完成Cloneable接口外面的clone辦法，而且在Copy外面的克隆辦法前往Student的一個克隆便可，如許便可以包管Student的獨一啦，修正以後的代碼以下：
public class DepthCopy {
public static void main(String[] args) {
Student student = new Student(95);
Copy first = new Copy("hzw", 24,student);
Copy second = null;
try {
second = (Copy) first.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
second.name = "shanxi";
second.student.score = 60;
System.out.println(first == second);//false
System.out.println(first.student == second.student);//false
System.out.println(first.student.score);//95
System.out.println(second.student.score);//60
}
}
class Copy implements Cloneable
{
public String name;
public int age;
public Student student;
public Copy(String name,int age,Student student) {
this.name = name;
this.age = age;
this.student = student;
}
@Override
protected Object clone() throws CloneNotSupportedException {
Copy copy = (Copy)super.clone();
copy.student = (Student) student.clone();
return copy;
}
}
class Student implements Cloneable
{
public int score;
public Student(int score) {
this.score = score;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
可以看到此時first和second和first.student和second.student都不是雷同的，是以我們修正second的student的score以後並沒有影響到first裡的student的score值，到達了深拷貝的目標；
然則，細心一想成績就出來了，假設我們下面例子的Student類中也存在援用類型的屬性，好比College類，那末我們必需讓College類完成Cloneable接口，然後在Student類外面的clone辦法外面挪用College類的clone辦法，在Copy類的clone辦法中挪用Student類的clone辦法，發明沒有了，這個進程好龐雜，必需讓類中的有關援用類型全體完成Cloneable接口，感到好費事是否是，好的，接上去就該牛人退場了；
處理深拷貝成績最好的方法就是采取序列化方法，如許各類類均不消完成Cloneable接口的，直接序列化反序列化便可以啦，我們來見識下吧。
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
public class DepthCopy {
public static void main(String[] args) {
College school = new College("nongda");
Student student = new Student(95, school);
Copy copy = new Copy("hzw",23, student);
Copy another = null;//表現反序列化出來的類實例
//停止序列化操作
try {
FileOutputStream fos = new FileOutputStream(new File("d:/copy.txt"));
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(copy);
} catch (Exception e) {
e.printStackTrace();
}
//停止反序列化操作
FileInputStream fis;
try {
fis = new FileInputStream(new File("d:/copy.txt"));
ObjectInputStream ois = new ObjectInputStream(fis);
another = (Copy) ois.readObject();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(copy == another);//false
System.out.println(copy.student == another.student);//false
System.out.println(copy.student.school == another.student.school);//false
another.student.school.schoolName = "wuda";
System.out.println(copy.student.school.schoolName);//nongda
}
}
class Copy implements Serializable
{
public String name;
public int age;
public Student student;
public Copy(String name,int age,Student student) {
this.name = name;
this.age = age;
this.student = student;
}
}
class Student implements Serializable
{
public int score;
public College school;
public Student(int score,College school) {
this.score = score;
this.school = school;
}
}
class College implements Serializable
{
public String schoolName;
public College(String schoolName) {
this.schoolName = schoolName;
}
}
從輸入便可以看出來，反序列化以後生成的對象完整就是對原對象的一份拷貝，除屬性值雷同以外其實不和原對象有任何干系，是以當我們修正反序列化生成對象的schoolName為"wuda"的時刻並沒有修正本來實例的schoolName值，照樣輸入"nongda",是以到達了真實的深拷貝後果，然則要想完成序列化，一切的有關類都必需完成Serializable接口，這總也比既完成Cloneable接口又完成clone辦法更便利吧。
以上就是對Java 深拷貝和淺拷貝的具體講授，有須要的可以參考下。
