java中深复制知识点详解

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);
  }
}

{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}}

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;
}

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();

  }
}