Written by Ivan Sutherland in 1963, Sketchpad was the first computer program to ever use a Graphical User Interface (GUI). It was considered to be useful for both artistic and technical purposes. It is also widely considered the precursor to the modern-day Computer Aided Design systems. It worked using the recently invented "light pen" and ran on the Lincoln TX-2 at MIT.
Developed by the Norwegian Computing Centre in the 1960's, Simula was a programming language that introduced the Object-Oriented Programming Paradigm. It is considered the precursor to all class-based class-based object oriented programming languages. As its name suggests, it was developed for simulations.
Squeak and Smalltalk both took influences from Sketchpad and Simula.
OOP became mainstream majorly from the introduction of C++ and GUI's in the mid-1980's. Supposedly, this paradigm is well-suited for GUI's.
They are similar in the fact that they both use a virtual machine and are both object-oriented programming languages. They are different in the fact that Java is more of a "industrial strength" language and SmallTalk is more suited and used for research purposes. SmallTalk is a simplistic syntax language and requires little to no knowledge of syntax learning curve, while Java has quite a bit of syntax rhetoric. SmallTalk is dynamically typed, while Java is casted. Java was developed by Sun Microsystems, while Smalltalk was developed by only a handful of people.
|BTW, just because Squeak is not "industrial strength", it doesn't mean others aren't. VisualWorks for instance is probably more robust than any Java implementation.|