molarmass

I got bored in chem.

I honestly could have made something like my saved-posts project where everything was practically in a single class, but I decided not to.

In fact, I also decided to purposely over-engineer and incorporate BDD into the development process, just cause why not?

Essentially, what this project is intended to do is to find the molar mass of a given formula of a substance.

Design

The string is parsed using a state-machine-like system, based on the last token parsed. The tokens can be a begin element state, which will accept the second and third lowercase letters as needed, which can be followed by an end group or begin group state, depending on the token.

The final result of the parser is a tree of values that is possible to reverse back into the original formula entered into the parser. The tree begins with a root node, which children consisting of the elements and any outermost groups and their associated subscripts.

Groups are parsed by using a placeholder to hold all the child elements until the subscript is parsed, in which case the token is then replaced with a subscript node.

The molar mass can then be found by recursing over the children of the root node, and their quantities can be found by using the getCount(int) method to parse the previous branch's count into the current node's count.

Building

git clone https://github.com/caojohnny/molarmass.git
cd molarmass
mvn test install

Executable jar will be located in ./target

You may also download the jar from here.

Use

Simple CLI interface. Begin the program, type in chemical formula. The correct capitalization is required, subscripts are normal numbers. For example, Barium hydroxide is Ba(OH)2.

If the correct formatting is used, the parser will accept the substance as valid, even if the elements don't work together. For example, HC2 will be valid, even though it is not possible (as far as I am aware) for it to form naturally.

Demo

Loading config...
Loading periodic table data...
> Ba(OH)2
Molar Mass: 171.3417 g/mol

> H2O
Molar Mass: 18.015 g/mol

> H2
Molar Mass: 2.016 g/mol

> H
Molar Mass: 1.008 g/mol

> 

Credits

Built with IntelliJ IDEA

Cucumber for BDD

Bowserinator's Periodic Table for the data