Merge level 10

There are a few methods in Parser that will be invalid if the user
inputs are not in the correct format.

Using assertions to define assumptions about the program state so that the runtime can verify them allows bugs in the code to be detected.

Let's define assertions to ensure that assumptions in the program are
not violate.

Add assertions to Parser methods

There are redundant comments and code duplication.

Improving code quality is important to make the code more understandable
so that it can be read, understood and modified by other developers.

Lets
* remove redundant comments
* minimize code duplication
* format Javadocs to follow coding standards

Improve code quality

Improve code quality

Add Better Search function