This is the code: I do not understand the keyword this in this context. It seems that it does not make any sense. You could write the following code: The result is the same, it prints 5. It seems to make no sense to use the keyword this, you can omit it. It is allowed to use the keyword this in this context, thus there must be a reason.
The line: is checking current instance of class with the other (other is also an instance of IntVector class).
You using this keyword to specify that the variable you are using is belong to current class.
For example with a setter method:
In that you let the compiler know what 'a' is variable of current class and what 'a' is the parameter.