java中深复制知识点详解

java中深复制知识点详解

在正式开始深复制的讲解之前，我们先来理解一下概念。假设一个物品需要批量生产，但是这个物品还配有赠品，生产的时候需要把赠品也列在计划内。所谓深复制的原理就是这样，我们不能只复制属性，包括引用之类的附带也需要被复制。下面就为大家带来深复制的两种不同方法。

1.序列化实现

如下为谷歌Gson序列化HashMap，实现深度复制的例子：

public class CopyDeepMapTest {

public static void main(String[] args) {

HashMap userMap = new HashMap<>();

userMap.put(1, new User("jay", 26));

userMap.put(2, new User("fany", 25));

//Shallow clone

Gson gson = new Gson();

String jsonString = gsonhttp://.toJson(userMap);

Type type = new TypeToken>(){}.getType();

HashMap clonedMap = gson.fromJson(jsonString, type);

//Same as userMap

System.out.println(clonedMap);

System.out.println("\nChanges DO NOT reflect in other map \n");

//Change a value is clonedMap

clonedMap.get(1).setName("test");

//Verify content of both maps

System.out.println(userMap);

System.out.println(clonedMap);

}

}

运行结果：

{1=User{name='jay', age=26}, 2=User{name='fany', age=25}}

Changes DO NOT reflect in other map

{1=User{name='jay', age=26}, 2=User{name='fany', age=25}}

{1=User{name='test', age=26}, 2=User{name='fany', age=25}}

从运行结果看出，对cloneMap修改，userMap没有被改变，所以是深度复制。

2.list深复制

两个list数据相同但是地址值不同，A和B是独立的两个list，A改变了B不会改变，B改变了A也不会改变

深复制的工具类方法:

public static List deepCopy(List src) throws IOException, ClassNotFoundException {

ByteArrayOutputStream byteOut = new ByteArrayOutputStream();

ObjectOutputStream out = new ObjectOutputStream(byteOut);

out.writeObject(src);

ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());

ObjectInputStream in = new ObjectInputStream(byteIn);

@SuppressWarnings("unchecked")

List&http://lt;T> dest = (List) in.readObject();

return dest;

}

关于深拷贝的一个扩展实例：

public class YuelyLog implements Serializable,Cloneable {

private Attachment attachment;

private String name;

private String date;

@Override

protected YuelyLog clone() throws CloneNotSupportedException {

return (YuelyLog)super.clone();

}

public Attachment getAttachment() {

return attachment;

}

public void setAttachment(Attachment attachment) {

this.attachment = attachment;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getDate() {

return date;

}

public void setDate(String date) {

this.date = date;

}

/**

* 使用序列化技术实现深拷贝

* @return

*/

public YuelyLog deepClone() throws IOException,Clashttp://sNotFoundException{

//将对象写入流中

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);

objectOutputStream.writeObject(this);

//从流中取出

ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStream.toByteArray());

ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);

return (YuelyLog)objectInputStream.readObject();

}

}

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