Java toString for debugging or actual logical use

Question

This might be a very basic question, apologies if this was already asked. Should toString() in Java be used for actual program logic or is it only for debugging/human reading only. My basic question is should be using toString() or write a different method called asString() when I need to use the string representation in the actual program flow.

The reason I ask is I have a bunch of classes in a web service that rely on a toString() to work correctly, in my opinion something like asString() would have been safer.

Thanks

Answer 1

Except for a few specific cases, the toString should be used for debugging, not for the production flow of data.

The method has several limitations which make it less suitable for use in production data flow:

• Taking no parameters, the method does not let you easily alter the string representation in response to the environment. In particular, it is difficult to format the string in a way that is sensitive to the current locale.
• Being part of the java.Object class, this method is commonly overridden by subclasses. This may be harmful in situations when you depend on the particular representation, because the writers of the subclass may have no idea of your restrictions.

The obvious exceptions to this rule are toString methods of the StringBuilder and the StringBuffer classes, because these two methods simply make an immutable string from the mutable content of the corresponding object.