java中深复制知识点详解
作者：小妮浅浅
在本篇文章里小编给大家整理了关于java中深复制知识点详解内容，有需要的朋友们可以学习下。
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。下面小编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<Integer, User> 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 = gson.toJson(userMap);
Type type = new TypeToken<HashMap<Integer, User>>(){}.getType();
HashMap<Integer, User> 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 <T> List<T> deepCopy(List<T> 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<T> dest = (List<T>) 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,ClassNotFoundException{
//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();
}
}