在正式開始深復(fù)制的講解之前，我們先來理解一下概念。假設(shè)一個物品需要批量生產(chǎn)，但是這個物品還配有贈品，生產(chǎn)的時候需要把贈品也列在計劃內(nèi)。所謂深復(fù)制的原理就是這樣，我們不能只復(fù)制屬性，包括引用之類的附帶也需要被復(fù)制。下面小編就為大家?guī)砩顝?fù)制的兩種不同方法。

如下為谷歌Gson序列化HashMap，實現(xiàn)深度復(fù)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); }}

運行結(jié)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}}

從運行結(jié)果看出，對cloneMap修改，userMap沒有被改變，所以是深度復(fù)制。

兩個list數(shù)據(jù)相同但是地址值不同，A和B是獨立的兩個list，A改變了B不會改變，B改變了A也不會改變

深復(fù)制的工具類方法:

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;}

關(guān)于深拷貝的一個擴展實例：

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; } /** * 使用序列化技術(shù)實現(xiàn)深拷貝 * @return */ public YuelyLog deepClone() throws IOException,ClassNotFoundException{ //將對象寫入流中 ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream); objectOutputStream.writeObject(this); //從流中取出 ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStream.toByteArray()); ObjectInputStream objectInputStream = new ObjectInputStream(inputStream); return (YuelyLog)objectInputStream.readObject(); }}