Control Flow: Overview

Welcome to Chapter 2. With First Steps behind you — values, numbers, text, I/O — these six lessons give a program the power to decide and to repeat. That's the point where it stops being a calculator and starts being software. You'll make choices with boolean logic and if/switch, repeat work with loops, steer that repetition with break/continue, store many values in arrays, and package logic into reusable methods.

There are six lessons, in this order:

1. Booleans & Logic — the yes/no type with no truthiness, comparisons, &&/||/!, and short-circuit evaluation as a guard.
2. Conditionals — if/else if/else, the switch statement and its fall-through trap, exhaustive switch expressions, and the ternary ?:.
3. Loops — while, do-while, the classic for, and the enhanced for, plus the off-by-one and infinite-loop traps.
4. Loop Control & Patterns — break, continue, labeled break, and the accumulation idioms most loops are built from.
5. Arrays — a fixed block of indexed slots, bounds checking at run time, iteration, jagged 2D arrays, and why an array isn't a growable list.
6. Methods — parameters, return types, void, overloading, and Java's pass-by-value rule (including how object references are passed by value).

Every code block with a ▶ Run button is live — change it, run it again, and watch what the compiler or the JVM says. The fastest way to learn in this chapter is to perturb working examples: move a break, flip a < to <=, forget a return, and see exactly which kind of error you get, compile-time or run-time.