How to clone an Object without knowing the exact type in Java?

Question

public void test(Object obj){`
      Object newObj = obj;//reference

}

Without knowing the exact type of obj, how could I clone it such as something as Object newObj = obj.clone(); or Object newObj = new Object(obj);

The actual situation is: in a class Message I set a member HashMap<String,Object> to allow anyone which wanna use Message can add other properties/members instead of rewriting it. The object may be ArrarList<Integer> . Here comes the problem.

Answer 1

A safe way is to serialize the object, then deserialize. This ensures everything is a brand new reference. You'll have to implement the Serializable interface.

Google commons class org.apache.commons.lang.SerializationUtils provides this for you via the following method:

SerializationUtils.clone(Object);

Example:

this.myObjectCloned = SerializationUtils.clone(this.object);

Answer 2

Simple: you can't do that.

Unless you know that all objects that you will ever process / encounter followes certain rules, for example they allow serialization.