Convert String into a Class Object

The Solution to Convert String into a Class Object is

I am storing a class object into a string using toString() method. Now, I want to convert the string into that class object.

Your question is ambiguous. It could mean at least two different things, one of which is ... well ... a serious misconception on your part.

If you did this:

SomeClass object = ...
String s = object.toString();

then the answer is that there is no simple way to turn s back into an instance of SomeClass. You couldn't do it even if the toString() method gave you one of those funky "[email protected]" strings. (That string does not encode the state of the object, or even a reference to the object. The xxxxxxxx part is the object's identity hashcode. It is not unique, and cannot be magically turned back into a reference to the object.)

The only way you could turn the output of toString back into an object would be to:

  • code the SomeClass.toString() method so that included all relevant state for the object in the String it produced, and
  • code a constructor or factory method that explicitly parsed a String in the format produced by the toString() method.

This is probably a bad approach. Certainly, it is a lot of work to do this for non-trivial classes.

If you did something like this:

SomeClass object = ...
Class c = object.getClass();
String cn = c.toString();

then you could get the same Class object back (i.e. the one that is in c) as follows:

Class c2 = Class.forName(cn);

This gives you the Class but there is no magic way to reconstruct the original instance using it. (Obviously, the name of the class does not contain the state of the object.)

If you are looking for a way to serialize / deserialize an arbitrary object without going to the effort of coding the unparse / parse methods yourself, then you shouldn't be using toString() method at all. Here are some alternatives that you can use:

  • The Java Object Serialization APIs as described in the links in @Nishant's answer.
  • JSON serialization as described in @fatnjazzy's answer.
  • An XML serialization library like XStream.
  • An ORM mapping.

Each of these approaches has advantages and disadvantages ... which I won't go into here.

~ Answered on 2011-03-23 06:46:33

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