The helpers.Helper methods are there to check which type an expression returns. They are always correct, so you don't need to check for mistakes over there. So if, for instance, you see:

import helpers.Helper;

or

Helper.GET_TYPE(3 * 4);

You don't have to check for errors. The GET_TYPE method will return the type of the expression passed as a parameter.

These exercises don't handle the access modifiers handled in chapter 4:

• private
• default (package private)
• protected
• public

Make sure you don't forget to train on them using other resources.

Using the java-terminal.sh you can execute one-liners to test certain expressions.

bash java-terminal.sh # PRESS ENTER
> System.out.println("Hello"); # PRESS ENTER
Hello

To just start practicing, run

bash ./run.sh train

This will show you Java 1.8 code, which you can analyse and think about how the compiler will handle it. When you think what will happen, you just press a button and the compiler will show what he makes of it.

After you've seen the result, press another button to continue to the next code fragment.

To run exercises from a specific chapter, just type

bash ./run.sh [chapter_number]

where [chapter_number] is the number of the chapter you want to train. you can also type random to get a random chapter.

To run specific exercises, just type

bash ./run.sh [chapter_number] [exercise_number]

where [chapter_number] is the number of the chapter you want to train and [exercise_number] is the number of the exercise you want to train. You can also type random.