the basics

variables, types, control flow, methods, and the stack/heap mental model everything else sits on.

1. 01variables and primitiveseight primitive types, how many bits each one gets, and what that means.
2. 02operatorsprecedence, short-circuiting, and the ++i vs i++ thing.
3. 03casting and overflowwidening, narrowing, and why Integer.MAX_VALUE + 1 is negative.
4. 04floating pointwhy 0.1 + 0.2 != 0.3, IEEE 754 bit by bit, and when to reach for BigDecimal.
5. 05strings, the basicsstring literals, immutability, concatenation and text blocks.
6. 06control flowif, loops, break, continue, and labeled breaks (yes, java has those).
7. 07switchthe old fallthrough switch vs the new arrow switch expression.
8. 08arraysfixed-size boxes in a row. 2d arrays are arrays of arrays (literally).
9. 09methodsparameters, return values, overloading and varargs.
10. 10the call stack and recursionevery call pushes a frame. watch them stack up and unwind.
11. 11stack and heapwhere your variables live vs where your objects live. the most important picture in java.
12. 12java is pass-by-valuealways. even for objects. here's the proof, step by step.
13. 13varlocal type inference: what it infers, and where it isn't allowed.
14. 14reading and printingSystem.out, printf formatting, Scanner and IO.println.