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elephantoo

Java

Strongly typed, object-oriented and everywhere — from Android to banking back-ends.

A complete, job-ready Java course built on Java 21 LTS. Start from zero with the JDK, variables, loops, methods, arrays and strings; master object-oriented design with classes, inheritance, interfaces, records and enums; handle errors and data with exceptions, generics and the Collections framework; then level up with lambdas, streams, file I/O, multithreading, the JVM memory model, JDBC with MySQL, Maven/Gradle, JUnit 5 and modern Java 17-21 features — finishing with your first step into Spring Boot.

43 lessons ~10 h 53 min Beginner → Advanced

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What you’ll learn

  • Install a JDK 21, and compile, run and debug Java programs from the terminal
  • Write clean procedural code with types, operators, control flow, loops, methods, arrays and strings
  • Design object-oriented programs with classes, encapsulation, inheritance, polymorphism, interfaces, records and enums
  • Handle failures robustly with checked/unchecked exceptions, custom exceptions and try-with-resources
  • Use generics and the Collections framework (List, Set, Map, Comparator) and implement equals/hashCode correctly
  • Process data declaratively with lambdas, method references, the Streams API, Optional and java.time
  • Read and write files with java.nio and build safe concurrent code with threads, executors, CompletableFuture and virtual threads
  • Explain JVM memory and garbage collection, and connect to MySQL with JDBC using PreparedStatement and transactions
  • Build and test real projects with Maven or Gradle and JUnit 5
  • Apply modern Java 17-21 features (sealed types, pattern matching, text blocks) and take your first steps with Spring Boot

Syllabus

6 modules · 43 lessons
  1. 1Introduction, JDK & JVMWhat Java is, how the JDK, JRE and JVM fit together, installing JDK 21 and your first program.
  2. 2Variables & data typesPrimitive types, Strings, var, casting and the integer-division trap.
  3. 3Operators & expressionsArithmetic, assignment, increment, comparison, logical and ternary operators, plus precedence.
  4. 4Reading input with ScannerRead numbers, words and whole lines from the keyboard, and avoid the nextInt/nextLine trap.
  5. 5Decisions: if/else & switchif, else if, else, nested conditions, the classic switch and modern switch expressions.
  6. 6Loops: for, while & do-whileCounted and conditional loops, the enhanced for, break, continue, labels and nested loops.
  7. 7MethodsParameters, return values, overloading, varargs, pass-by-value, scope and recursion.
  8. 8ArraysCreate, loop over, copy, sort and search arrays, plus 2D arrays and the Arrays helper class.
  9. 9Strings & StringBuilderString methods, immutability, comparison, formatting, text blocks and fast building with StringBuilder.
  1. 10Classes & objectsFields, methods, creating objects with new, references, null and toString.
  2. 11Constructors & thisDefault and parameterised constructors, overloading, this(...) chaining and initialisation order.
  3. 12The static keywordStatic fields, methods, constants, static blocks, nested classes and when to use each.
  4. 13Encapsulation & access modifiersprivate, package-private, protected and public; getters, setters, validation and immutable classes.
  5. 14Inheritanceextends, super, constructor chaining, the Object class, final classes and composition vs inheritance.
  6. 15Polymorphism: overriding & overloadingDynamic dispatch, @Override rules, overloading resolution, upcasting, downcasting and instanceof.
  7. 16Abstraction & abstract classesAbstract methods and classes, template methods and when abstraction helps.
  8. 17InterfacesContracts, multiple implementation, default, static and private methods, and interface vs abstract class.
  9. 18RecordsConcise immutable data carriers: components, compact constructors, methods and limitations.
  10. 19EnumsType-safe constants with fields, constructors, methods, switch, values(), EnumMap and EnumSet.
  11. 20Packages, imports & JARsOrganise code into packages, import classes, compile multi-package projects and build a JAR.
  1. 21Exception handlingtry/catch/finally, the exception hierarchy, checked vs unchecked, throw, throws and multi-catch.
  2. 22Custom exceptions & try-with-resourcesDesign your own exceptions, chain causes, and close resources automatically with AutoCloseable.
  3. 23Wrapper classes & autoboxingInteger, Double and friends, parsing, autoboxing/unboxing, caching and null pitfalls.
  4. 24GenericsGeneric classes and methods, type parameters, bounded types, wildcards and type erasure.
  5. 25Collections & ListsThe Collections framework, ArrayList vs LinkedList, Iterator, removeIf, immutable lists and queues.
  6. 26Sets: HashSet & TreeSetUnique elements with HashSet, LinkedHashSet and TreeSet, set algebra and navigation.
  7. 27Maps: HashMap & TreeMapKey-value storage, iteration, getOrDefault, merge, computeIfAbsent, TreeMap and LinkedHashMap.
  8. 28Comparable vs ComparatorNatural ordering with compareTo, custom orderings with Comparator.comparing, thenComparing and reversed.
  9. 29equals() & hashCode()The equality contract, writing correct equals/hashCode, and why HashMap breaks without them.