Install JDK 21, configure IntelliJ IDEA, understand the compile-run cycle, and write a working Hello World that exercises println, static methods, and command-line args.

Declare and use all 8 primitive types, understand autoboxing, use all comparison/logical operators correctly, and implement if/switch/for/while/do-while without reference.

Write methods with proper return types, understand parameter passing, define a class with private fields and public methods, and use this keyword and constructors correctly.

Create a class hierarchy using extends, override methods polymorphically, declare abstract classes, implement interfaces, and understand when to choose each.

Use ArrayList and HashMap fluently, understand generics, apply the 5 core Stream operations (filter, map, sorted, collect, reduce), and choose the right collection for a task.

Handle checked and unchecked exceptions correctly, create custom exception classes, use try-with-resources for file safety, and read/write text and CSV files with java.nio.file.Files.

Use val/var correctly, define data classes, write null-safe code with ? and !!, use extension functions to add behavior to existing classes, and write when expressions.

Design and implement a Contact class hierarchy, a ContactBook with full CRUD, search/filter with Streams, sort by multiple fields, serialize to/from JSON-style text, and test edge cases.