The basic ideas of object technology can be (and are) realised in different ways. As usual with the implementation of any ideas, compromises are needed. Two computer programming languages which implement object concepts in different ways are Smalltalk and Java.

In Smalltalk there are only objects, messages and variables, and they work entirely uniformly. In Smalltalk, even classes are available as objects. In Smalltalk, all classes can be subclassed, and all inherited methods can be overridden. In Java, primitive types and operations are provided, so there are ways other than objects to represent information. In Java, classes or methods can be marked as final and so not subclassed or overridden.