Java is a product of Oracle and they have provided this tutorial on their website.
W3 Schools is an extensive website providing tutorials for many languages and apps. This is their turorial for Java.
Matlab
Matlab was invented by Cleve Moler and released by Mathworks. They have an extensive tutorial on their website.
Microsoft Excel
This is an Excel tutorial provided by W3 Schools.
One of the popular websites for learning Excel is called Excel Easy.
Python
The Python organization has this tutorial on their website.
W3 Schools has a Python tutorial on their very extensive website.
R Studio
W3 Schools has an R tutorial on their website.
Mathematica
Wolfram has a Mathematica tutorial on their website.