Java Foundations: The Complete Course with Java 21 Updates

Learn how to use varargs in Java to pass a variable number of arguments to a method, comparing to arrays, using ellipses, and accessing elements.

Master removing whitespace in Java by using strip and trim to clean leading and trailing spaces, and explore strip leading, strip trailing, and strip indent with text blocks.

Discover how the Java contains method checks if a string includes a given sub string with exact matches, using seven in four score and seven years ago as an example.

Learn how the endswith and startswith methods verify file name patterns, such as ensuring a string ends with .txt and begins with file, return booleans, and demonstrate method chaining.

Use contentEquals to compare string contents for equality across strings, string buffers, and string builders. Discover how contentEquals handles character sequences and returns booleans, and how it differs from equals.

Learn to use capture groups in regex to extract phone-number digits, including country code up to two digits, area code, exchange, and line number.

Expand phone number parsing to accept optional parentheses and country code in North American formats using escaped parentheses and optional groups.

Learn how regex in Java uses the dot to match any character, anchors like caret and dollar, and classes such as word, digit, and non-space, with boundary and ASCII notes.

Learn to find multiple matches in a multi-line string with Java's regex engine, using Pattern and Matcher, named capture groups, and start/end indexes.

Explore hexadecimal, a base-16 system using 0–9 and A–F, and how it compresses binary and decimal data. See nibble concepts, byte alignment, and memory addresses represented in hex.

Explore how floating point numbers are stored in memory, compare float and double, and learn why binary representation yields approximation that impacts money calculations.

Move beyond Math.random by using java.util.Random, call nextInt with an upper bound, and optionally seed the generator; for stronger needs, try SecureRandom with a byte[] seed.

Translate physics formulas into Java by computing path velocity, centripetal acceleration, and centripetal force through modular, overloaded methods using mass, radius, and period.

compare numbers in Java using equals (==) and not equals (!=), differentiate from the assignment operator (=), and cover greater than or equal to, less than or equal to checks.

Discover how BigDecimal fixes precision issues when using float or double by instantiating with strings for exact values, and use its methods like subtract for precise decimal arithmetic.

Explore key big decimal methods for precise math, including add, subtract, multiply, divide with math context, and handling non-terminating decimals. Learn sqrt, max and min, absolute value, and remainder operations.

Explore how to instantiate big decimal and big integer, including string vs primitive constructors, and learn about precision loss when using doubles, plus conversions to byte, int, and string.

Develop a Java compound interest calculator using BigDecimal to compute future balance from principal, rate, years, and annual contributions, applying the one plus rate to the power of years.

Explore inequalities in conditionals with if-else statements, use relational operators, and combine conditions with logical and and logical or, plus modulo, to classify numbers and set colors.

Demonstrates using the switch statement to route on a value with cases and breaks, including default, illustrated with numbers and strings, and contrasts with if-else and null handling.

Showcase switch expressions in java 14, using arrow syntax and yield to return values, including blackjack card value logic, ace handling, and parsing integers from cards.

Explore test-driven development by creating a second unit test for adding numbers, running tests, and refining code to pass while reducing duplication through setup and refactoring.

Analyze how to test randomness in a Java number-guessing game by using an array tally approach to verify a fair 1–10 number spread.

Learn how to debug Java code with an IDE by setting breakpoints, stepping through lines, inspecting variables, and reloading changed classes during debugging.

Master debugging with breakpoints, conditional stops, and view breakpoints; learn when to step over, avoid third-party code, and reinforce bugs with tests and automated builds.

Revisit object-oriented concepts like classes and models to deepen your understanding of Java's power. Explore remaining concepts to unlock foundational skills and elevate your Java development.

Introduce four role specific classes, programmer, manager, analyst, and CEO, to refactor the salary program from procedural to object oriented, with constructor based parsing and a get salary method.

Refactor by creating a base employee class and pull up common fields, reducing duplication among programmer, manager, analyst, and CEO, while updating constructors and using extends and protected members.

Learn how to extract responsibilities from a main class by introducing a factory method on the employee class to instantiate role-based subclasses, simplifying code and improving maintainability.

Explore nested classes in Java, comparing static nested classes and inner classes, and learn about anonymous and local nested classes, including when to use each for accessing enclosing fields.

Use instanceof and pattern matching to differentiate programmer and manager outputs while iterating employees, replacing get class checks with type aware printing in Java 16.

Explore the new features of Java 21, including switch pattern matching, records for programmer data, and unnamed patterns to simplify guards on lines of code per day.

Explore how to model a chessboard in Java, including a chessboard class, chess piece hierarchy, and coordinates, and walk through adding and retrieving pawns using chess notation like A2.

Explore implementing knight move validation in a Java chess board, including preventing moves to invalid squares, blocking friendly occupancy, and capturing enemy pieces with captured piece tracking.

Discover how Java collections store objects with dynamic size, compare them to arrays, and explore the collections framework’s interface-driven hierarchy from list to map.

Explore lists as dynamic, ordered collections that grow beyond arrays, use generics to store employees safely, and iterate with enhanced for loops to total salaries.

Learn quick list creation with array list and list.of, and remove items by object or index, while exploring iterator use and basic patterns across lists, sets, and maps.

Explore advanced list methods in Java, including add at a specific index, add all, contains, indexOf and lastIndexOf, remove, subList, retain all, set, toArray conversions, and unmodifiable lists via List.of.

Sort lists with the list sort method and a comparator, using anonymous classes or lambdas, and explore Arrays.sort and Collections.sort. Implement comparable for natural ordering in strings and employees.

Explore the set interface and learn how hash sets prevent duplicates, compare them with lists, and understand hash codes, contains checks, and the performance implications.

Learn how a linked hash set preserves insertion order while filtering duplicates via equals and hashCode, and compare it to hash set's performance and lack of random access.

Explore how the TreeSet filters duplicates and orders items using a comparable implementation or a comparator, illustrating how last name versus first name affects results.

Explore how maps in the Java collections framework store key-value pairs, enabling lookups and data association, with common implementations: hash map, tree map, and linked hash map.

Learn how to implement a get salary method in a Java main class, write JUnit 5 tests, and switch from list traversal to a hash map for fast lookups.

Transform lookups by building a map from first names to salaries, using hash map, tree map, or linked hash map; observe how keys update with duplicates and retrieval is fast.

Explore common map methods in Java, including get, put, values, keySet, entrySet, containsKey, getOrDefault, isEmpty, putIfAbsent, remove, and putAll, with examples showing insertion order and entry iteration.

Explore the streams api by re-implementing text processing with lines into employee objects using map, forEach, and method references, showcasing lambdas and a pipeline approach.

Explore how to create streams from collections and arrays, use stream, of, range, and boxed methods, map operations, and read lines from files.lines, including null handling and empty streams.

Learn to sum employee salaries with the streams API by mapping text to employee objects and then to salaries. Use mapToInt and sum to compute total, and print the results.

Learn to use streams API to sum salaries by mapping arrays to a domain model, then collect results using a record-based person.

Group records by state using the collect method’s grouping by, returning a map of string to list of person, and alphabetize results with a tree map, illustrated with spreadsheet visuals.

Learn to group data by a field and apply summing and formatting with Java collectors, producing a state-to-salary map and neatly formatted key-value results.

Learn to nest grouping by state and gender in Java streams, aggregate salaries, and format results as currency using a tree map.