Learn5 lessons
Java
Classes, collections, interfaces and exceptions — the object model an interview actually probes, with the mistakes almost everyone makes once.
In this course
- Primitives, wrappers, and the == trapWhy int and Integer are not interchangeable, and the caching quirk that makes == look like it works.7 min
- equals, hashCode, and the contract between themWhy overriding one without the other breaks every hash-based collection silently.8 min
- Lists, sets, maps, and picking the right oneArrayList against LinkedList, HashMap against LinkedHashMap and TreeMap, and what each one actually costs.8 min
- Interfaces, abstract classes, and polymorphismWhat each one can do that the other cannot, and why calling through an interface is the default.8 min
- Checked exceptions, unchecked exceptions, and try-with-resourcesThe one real difference between the two families, and the resource leak try-with-resources exists to prevent.8 min