Lessons

Does a math degree give an edge when learning programming? Everything depends on how much effort you put into related subjects. This is the story of Roman, who is from Kharkov. Today he is a senior Java developer. In mid-2015, he was a student working on a master's degree in applied...

For a beginner, the ArrayList class is aerobatics! This topic usually comes much later, but here at the secret CodeGym center we decided not to drag out the Cat cat = new Cat() by the tail. So we created an overview of ArrayLists for the very first quest. Here we'll try to explain what kind of class ArrayList is and compare it with ordinary arrays.

We're strictly adhering to the methodology adopted by the secret CodeGym training center: learn information and then practice using it. The now incomprehensible and complex phrase ArrayList<String> list = new ArrayList<>() will soon become instinctive and clear. As plain as «Hello, I'm a list of strings. You can call me 'list'».

According to Wikipedia, a generic is a drug sold under an international non-proprietary name or under a proprietary name different from the brand name. In Java, generics… Uh...are in no way related to generic drugs. They're just types with a parameter.

You will be fully immersed in Java generics and ArrayList during your second quest at the secret CodeGym center. But right now we'll slow become accustomed to these complex but essential structures, analyzing code snippets with detailed explanations from your teachers.

According to research performed by the secret CodeGym center in academic year 3099, ArrayList appears to be the most difficult topic for the students working on the first quest. One of... So don't idle your time away: take the bull by the horns and start completing tasks. The more tasks you do, the clearer ArrayList will become.

You already know a lot about primitive types, and in this level you got acquainted with their doppelgangers — the wrapper classes, and learned what autoboxing and unboxing are, how to compare wrapper types correctly, and how to do it incorrectly. You also took your array experience to the next level by getting to know...

Several tasks must be completed at the end of the level. Some of them are more advanced and require student's to be able to google. Or think. Or think and google. Practice completing them day in and day out, and your skills will grow at an incredible speed. They were created especially for IDEA.