Enthuware

Under section 4.1.2,Conventions in Java, it states that class names such as "Readonlyarraylist" is an incorrect way to declare a class name as it does not follow camel case convention

However, when typing

class Readonlyarraylist{} into eclipse, there is no issues being shown. Just wanted to get some clarity on this matter.

It is a convention, not a rule. Conventions are meant for human readability of the code and not for the compiler. Compiler doesn't care how you name your classes or variables.