← Back to all weeks

Week 02: Strings, Loops & Arrays

Interactive visuals, reference guides, exercise companions, and games for Strings, classes & objects, loops, arrays, and the IntelliJ debugger

Module 1 - Working with Strings

String Methods Explorer

Interactive sandbox: try length, trim, toUpperCase, charAt, indexOf, substring and more

String Immutability & StringBuilder

Why Strings create new objects on every change, and how StringBuilder avoids that

String Parsing: indexOf & substring

Character-by-character index view showing how to extract pieces from a string

String ↔ Number/Date Conversion

parseInt, parseDouble, LocalDate.parse with DateTimeFormatter patterns

Module 2 - Classes & Objects

Intro to Classes & Objects

Start here — why classes exist, what an object is, and how new turns a blueprint into real data

Classes & Objects: Blueprint vs Instance

A class is a blueprint — watch objects get created from it with the new keyword

Encapsulation: public vs private

Why fields are private, how getters and setters control access

Constructor Overloading

Multiple ways to create the same type of object — with and without parameters

Method Overloading

Same method name, different parameters — how Java picks the right one

Object Lifecycle

Create an object, call its methods, watch its state change step by step

Module 3 - Loops & Arrays

Loop Types: while vs do/while vs for

Side-by-side animation showing how each loop type executes

break vs continue

Step through a loop iteration by iteration — see exactly which ones run

Arrays: Memory & Indexing

Zero-based indexing, .length, default values — visual memory cells

for-each Loop vs for Loop

When you need the index vs when you just need the element

Array Operations

Sort, copy, pass to methods, return from methods — animated step by step

Workbook 2b - IntelliJ Debugger

IntelliJ Debugger Walkthrough

Breakpoints, step over/into/out, call stack, and watch variables in a mock IDE

Quick Reference Guides

Week 2 Cheat Sheet

Quick reference for Strings, classes, loops, and arrays — keep this open while you code

Glossary / Key Terms

All Week 2 vocabulary — searchable, with examples

Common Errors Guide

Top mistakes from Week 2 exercises — what went wrong and how to fix it

How to use IntelliJ's debugger — breakpoints, stepping, variables, and expressions

Exercise companions help you understand each exercise — what to build, what a successful run looks like, and which concepts you need. No solutions, no spoilers.

Workbook 2a - Strings

Full Name Generator

Build a full name from parts — handle optional middle name and suffix

Full Name Parser

Take a full name string and split it into first, middle, and last

Parse a formatted score string to find the winning team

Theater Reservations

Collect name, date, and tickets — parse and format the confirmation

Address Builder

Use StringBuilder to collect and format billing and shipping addresses

Workbook 2a - Classes & Objects

CellPhone Service

Create a CellPhone class with private fields, getters, setters, and a constructor

CellPhone Service 2 (Methods)

Add a dial() method and a static display() helper — objects interacting

CellPhone Service 3 (Overloading)

Add overloaded constructors and overloaded dial() methods

Workbook 2a - Loops & Arrays

Looping Exercises

Practice while, do/while, and for loops — three small programs

Roll two dice 100 times, count specific sums — classes, loops, and random numbers

Test Statistics

Calculate average, high, low, and median from an array of test scores

Vehicle Inventory

Menu-driven app to list, search, and add vehicles — arrays of objects

Workshop 2w

Neighborhood Library

Build a book checkout system — Book class, arrays, menu-driven flow

Practice what you learned with interactive games — test your knowledge, race the clock, and have fun.

Strings

String Method Match

Given a task, pick the right String method to use

Index Inspector

Predict what charAt(), indexOf(), and substring() return

Parse Challenge

Given parsing code and a formatted string, predict the output

Loops

Trace while, do/while, and for loops — predict iterations and output

Break or Continue?

Will this loop break, continue, or run normally? Predict the output

Arrays

Array Index Quiz

Given array operations, predict values at each index — watch for off-by-one

Classes & Objects

Constructor Picker

Which overloaded constructor gets called? Match the arguments

Can this code access that field or method? Test public vs private rules

Assemble a valid Java class — pick the right fields, constructor, getters, and methods

Mixed Review

Find the bug and pick the fix — Week 2 edition with String, loop, array, and OOP errors

Flashcard Quiz 2

Test your Week 2 vocabulary — OOP terms, String methods, loop and array concepts

Capstone

Debug Detective

Multi-step debugging scenario — find and fix bugs across classes in a broken app