Java使用序列化流實現對List泛型的深拷貝

使用序列化流實現對List泛型的深拷貝

深拷貝

• 爲新的對象重新開闢一個內存空間，拷貝原有對象的數據結構和值；新的對象的值修改不會涉及原對象的值（請注意性能問題）。

實現序列化拷貝的前提條件

• 實體對象實現Serializable接口

  /**
   * 用戶實體類
   */
  public class UserEntity implements Serializable {
  
      private int id;
  
      private String username;
  
      private String sex;
  
      private int age;
  
      private String address;
  
      private String birthday;
  
      //get、set方法省略
  	
      public UserEntity(int id, String username, String sex, int age, String address) {
          this.id = id;
          this.username = username;
          this.sex = sex;
          this.age = age;
          this.address = address;
      }
  
      @Override
      public String toString() {
          return "UserEntity{" +
                  "id=" + id +
                  ", username='" + username + '\'' +
                  ", sex='" + sex + '\'' +
                  ", age=" + age +
                  ", address='" + address + '\'' +
                  '}';
      }
  }
  

序列化拷貝方法

• private static final Logger LOGGER = LoggerFactory.getLogger(DeepCopyDemo.class);
  
  public static <T> List<T> deepCopy(List<T> list) {
          //判斷是否實現序列化
          if (list instanceof Serializable){
              ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
              try {
                  ObjectOutputStream out = new ObjectOutputStream(byteOut);
                  out.writeObject(list);
  
                  ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
                  ObjectInputStream inStream = new ObjectInputStream(byteIn);
                  List<T> ts = (List<T>) inStream.readObject();
                  return ts;
              } catch (Exception e) {
                  LOGGER.error("序列化Copy失敗", e);
                  e.printStackTrace();
              }
          }
          return null;
      }
  

序列化拷貝測試

• public static Integer INDEX  = 0;
  
      public static void main(String[] args) {
          UserEntity userEntity1 = new UserEntity(0, "張無忌","女",1 , "beijignshi");
          UserEntity userEntity2 = new UserEntity(1, "李尋歡","女",4 , "tianjinshi");
          UserEntity userEntity3 = new UserEntity(3, "項羽","男",0 , "chuguo");
          UserEntity userEntity4 = new UserEntity(4, "劉邦","男",8 , "hanchao");
  
          List<UserEntity> list = new ArrayList<>();
          list.add(userEntity2);
          list.add(userEntity1);
          list.add(userEntity4);
          list.add(userEntity3);
  
          System.out.println("----deep copy front----");
          for (UserEntity userEntity: list) {
              System.out.println(userEntity.toString());
          }
  
          List<UserEntity> copyResult = deepCopy(list);
          System.out.println("----deep copy after----");
          copyResult.get(INDEX).setUsername("夷陵老祖");
          for (UserEntity userEntity: copyResult) {
              System.out.println(userEntity.toString());
          }
  
      }
  

拷貝結果

• ----deep copy front----
  UserEntity{id=1, username='李尋歡', sex='女', age=4, address='tianjinshi'}
  UserEntity{id=0, username='張無忌', sex='女', age=1, address='beijignshi'}
  UserEntity{id=4, username='劉邦', sex='男', age=8, address='hanchao'}
  UserEntity{id=3, username='項羽', sex='男', age=0, address='chuguo'}
  ----deep copy after----
  UserEntity{id=1, username='夷陵老祖', sex='女', age=4, address='tianjinshi'}
  UserEntity{id=0, username='張無忌', sex='女', age=1, address='beijignshi'}
  UserEntity{id=4, username='劉邦', sex='男', age=8, address='hanchao'}
  UserEntity{id=3, username='項羽', sex='男', age=0, address='chuguo'}