Getting Started
This course is designed to take a learner from absolute beginner to advanced Java developer. You will start by understanding how Java works internally, then gradually move toward object-oriented programming, advanced language features, multithreading and memory management.
Each module builds on the previous one, ensuring a smooth learning curve. By the end of these modules, you will be able to:
- Understand how Java programs run inside the JVM
- Write clean, efficient Java code following industry standards
- Fully grasp OOP concepts and apply them in real projects
- Use advanced Java features like Streams, Lambdas, NIO, Optional, Records, and Virtual Threads
- Work confidently with data structures, algorithms, collections, and multithreading
- Understand JVM memory, class loading, and garbage collection
- Apply design patterns used in enterprise-level systems
- Become job-ready as an advanced Java developer
01 — Java Basics
Introduction to Java, how it works, essential concepts like variables, data types, input handling, and basic program structure.
02 — Operators
Understanding how Java performs calculations, comparisons, logical decisions, and evaluation order using different types of operators.
03 — Control Flow
Mastering decision-making tools like if-else, switch statements, loops, and flow-control techniques for building logical programs.
04 — Arrays
How to store multiple values, work with single and multidimensional arrays, iterate using loops, and use array utility methods.
05 — Methods and Constructors
Understanding reusable code blocks, method overloading, constructors, object initialization, and important keywords like this and super.
06 — Classes and Objects
Deep dive into OOP fundamentals, memory model (stack and heap), static members, object lifecycle, garbage collection, and Object class methods.
07 — Encapsulation
How to hide data using private fields, provide controlled access via getters/setters, use access modifiers, and build secure class structures.
08 — Inheritance
Building new classes from existing ones, understanding types of inheritance, method overriding, and runtime behavior through polymorphism.
09 — Polymorphism
Mastering compile-time and runtime polymorphism, method binding, and achieving dynamic behavior in Java programs.
10 — Abstraction and Interfaces
Understanding abstract classes, interfaces, multiple-type inheritance, functional interfaces, lambdas, and interface enhancements in modern Java.
11 — Inner Classes
Working with nested classes, method-local, static nested, and anonymous classes for event handling and structural organization.
12 — Enum and Annotation
Learning enumerations for fixed values and annotations for metadata, including built-in and custom annotation creation.
13 — Strings
Understanding string immutability, memory storage (pool), common methods, and mutable alternatives like StringBuilder and StringBuffer.
14 — Java Lang and Util APIs
Mastering important standard classes like Wrapper types, Math, System, Objects, Arrays, Collections, Date/Calendar, Random, UUID, and the Java Time API.
15 — Exception Handling
Learning error handling techniques, try-catch, multiple catches, finally, throw/throws, custom exceptions, and Java exception hierarchy.
16 — Collections Framework
Understanding List, Set, Map, Queue, and their implementations (ArrayList, HashSet, HashMap, TreeMap, PriorityQueue, etc.).
17 — Stream API
Using streams for functional programming, filtering, mapping, reducing, sorting, and working with parallel execution.
18 — Collection Internals
Deep dive into how collections work internally, including HashMap, ConcurrentHashMap, CopyOnWriteArrayList, fail-fast vs fail-safe, and LinkedHashMap.
19 — Concurrency Advanced
Mastering Executors, thread pools, Future, Callable, locks, semaphores, latches, barriers, atomics, and high-level concurrency utilities.
20 — JVM Internals
Understanding JVM architecture, class loading, JIT compilation, garbage collectors, memory leaks, and performance tuning.
21 — NIO
Learning buffers, channels, selectors, asynchronous IO, and high-performance file handling used in scalable systems.
22 — Modern Java Features
Features from Java 8 to Java 21 including Optional, Records, Sealed Classes, Enhanced Switch, Text Blocks, Pattern Matching, and Virtual Threads.
23 — File Handling
Reading and writing files, buffered streams, serialization, deserialization, and handling external data effectively.
24 — Design Patterns
Understanding essential object-oriented design patterns including Singleton, Factory, Builder, Prototype, Adapter, Observer, Strategy, and Decorator.
25 — Testing
Unit testing with JUnit, mocking with Mockito, and understanding the fundamentals of test-driven development.
26 — Build Tools
Learning project automation and dependency management using Maven and Gradle.
java/
├── 01-basics/
│ ├── 01-how-java-works.mdx
│ ├── 02-jdk-setup.mdx
│ ├── 03-jdk-jre-jvm.mdx
│ ├── 04-first-code.mdx
│ ├── 05-naming-convention.mdx
│ ├── 06-variables.mdx
│ ├── 07-data-types.mdx
│ ├── 08-literals.mdx
│ ├── 09-type-conversion.mdx
│ ├── 10-comments.mdx
│ ├── 11-keyboard-input-scanner.mdx
│ ├── 12-keyboard-input-bufferedreader.mdx
│ ├── 13-command-line-arguments.mdx
│ └── meta.json
│
├── 02-operators/
│ ├── 01-arithmetic-operators.mdx
│ ├── 02-relational-operators.mdx
│ ├── 03-logical-bitwise-operators.mdx
│ ├── 04-unary-operators.mdx
│ ├── 05-assignment-operators.mdx
│ ├── 06-ternary-operator.mdx
│ ├── 07-operator-precedence.mdx
│ └── meta.json
│
├── 03-control-flow/
│ ├── 01-if-else.mdx
│ ├── 02-nested-if.mdx
│ ├── 03-switch-statements.mdx
│ ├── 04-newer-switch.mdx
│ ├── 05-while-loop.mdx
│ ├── 06-do-while-loop.mdx
│ ├── 07-for-loop.mdx
│ ├── 08-enhanced-for-loop.mdx
│ ├── 09-break-and-continue.mdx
│ ├── 10-labels-in-java.mdx
│ ├── 11-which-loop-to-use.mdx
│ └── meta.json
│
├── 04-arrays/
│ ├── 01-need-of-array.mdx
│ ├── 02-array-basics.mdx
│ ├── 03-creation-of-array.mdx
│ ├── 04-array-iteration-techniques.mdx
│ ├── 05-drawbacks-of-array.mdx
│ ├── 06-array-of-objects.mdx
│ ├── 07-multi-dimensional-array.mdx
│ ├── 08-jagged-and-3d-array.mdx
│ ├── 09-arrays-class-methods.mdx
│ └── meta.json
│
├── 05-methods-and-constructors/
│ ├── 01-methods-in-java.mdx
│ ├── 02-method-overloading.mdx
│ ├── 03-varargs-in-java.mdx
│ ├── 04-static-method.mdx
│ ├── 05-this-keyword.mdx
│ ├── 06-super-keyword.mdx
│ ├── 07-constructors.mdx
│ ├── 08-default-vs-parameterized-constructor.mdx
│ ├── 09-constructor-chaining.mdx
│ ├── 10-copy-constructor.mdx
│ ├── 11-anonymous-object.mdx
│ └── meta.json
│
├── 06-classes-and-objects/
│ ├── 01-introduction.mdx
│ ├── 02-class-and-object-theory.mdx
│ ├── 03-class-and-object-practical.mdx
│ ├── 04-stack-and-heap.mdx
│ ├── 05-garbage-collection-and-finalize.mdx
│ ├── 06-static-variable.mdx
│ ├── 07-static-block.mdx
│ ├── 08-object-class-methods.mdx
│ ├── 09-cloneable-interface.mdx
│ ├── 10-packages-in-java.mdx
│ └── meta.json
│
├── 07-encapsulation/
│ ├── 01-encapsulation-concept.mdx
│ ├── 02-getters-and-setters.mdx
│ ├── 03-access-modifiers.mdx
│ ├── 04-data-hiding-vs-encapsulation.mdx
│ ├── 05-immutable-class.mdx
│ └── meta.json
│
├── 08-inheritance/
│ ├── 01-need-of-inheritance.mdx
│ ├── 02-what-is-inheritance.mdx
│ ├── 03-types-of-inheritance.mdx
│ ├── 04-multiple-inheritance.mdx
│ ├── 05-super-keyword-in-inheritance.mdx
│ ├── 06-upcasting-and-downcasting.mdx
│ ├── 07-dynamic-method-dispatch.mdx
│ ├── 08-has-a-vs-is-a-relationship.mdx
│ └── meta.json
│
├── 09-polymorphism/
│ ├── 01-polymorphism-overview.mdx
│ ├── 02-compile-time-polymorphism.mdx
│ ├── 03-run-time-polymorphism.mdx
│ ├── 04-binding-static-vs-dynamic.mdx
│ └── meta.json
│
├── 10-abstraction-and-interfaces/
│ ├── 01-abstract-class.mdx
│ ├── 02-abstract-method.mdx
│ ├── 03-interface-basics.mdx
│ ├── 04-need-of-interface.mdx
│ ├── 05-more-on-interfaces.mdx
│ ├── 06-types-of-interface.mdx
│ ├── 07-default-method-in-interface.mdx
│ ├── 08-static-method-in-interface.mdx
│ ├── 09-functional-interface.mdx
│ ├── 10-lambda-expression-basics.mdx
│ ├── 11-lambda-with-return.mdx
│ ├── 12-marker-interface.mdx
│ └── meta.json
│
├── 11-inner-classes/
│ ├── 01-inner-class.mdx
│ ├── 02-method-local-inner-class.mdx
│ ├── 03-static-inner-class.mdx
│ ├── 04-anonymous-inner-class.mdx
│ ├── 05-abstract-anonymous-inner-class.mdx
│ └── meta.json
│
├── 12-enum-and-annotation/
│ ├── 01-what-is-enum.mdx
│ ├── 02-enum-if-and-switch.mdx
│ ├── 03-enum-class.mdx
│ ├── 04-annotation-basics.mdx
│ ├── 05-built-in-annotations.mdx
│ ├── 06-custom-annotation.mdx
│ └── meta.json
│
├── 13-strings/
│ ├── 01-what-is-string.mdx
│ ├── 02-mutable-vs-immutable.mdx
│ ├── 03-stringbuffer-stringbuilder.mdx
│ ├── 04-string-methods.mdx
│ ├── 05-string-pool.mdx
│ ├── 06-string-performance.mdx
│ └── meta.json
│
├── 14-lang-and-util-apis/
│ ├── 01-overview-java-lang-and-java-util.mdx
│ ├── 02-wrapper-classes.mdx
│ ├── 03-math-class.mdx
│ ├── 04-system-and-runtime.mdx
│ ├── 05-objects-class.mdx
│ ├── 06-random-class.mdx
│ ├── 07-scanner-class.mdx
│ ├── 08-arrays-utility-class.mdx
│ ├── 09-collections-utility-class.mdx
│ ├── 10-date-and-calendar.mdx
│ ├── 11-java-time-api.mdx
│ ├── 12-optional-class.mdx
│ ├── 13-uuid-class.mdx
│ └── meta.json
│
├── 15-exception-handling/
│ ├── 01-what-is-exception.mdx
│ ├── 02-try-catch.mdx
│ ├── 03-multiple-catch.mdx
│ ├── 04-finally-block.mdx
│ ├── 05-try-with-resources.mdx
│ ├── 06-throw-vs-throws.mdx
│ ├── 07-custom-exception.mdx
│ ├── 08-exception-hierarchy.mdx
│ ├── 09-checked-vs-unchecked-exception.mdx
│ └── meta.json
│
├── 16-collections/
│ ├── 01-collection-framework-overview.mdx
│ ├── 02-list-interface.mdx
│ ├── 03-arraylist.mdx
│ ├── 04-linkedlist.mdx
│ ├── 05-set-interface.mdx
│ ├── 06-hashset.mdx
│ ├── 07-treeset.mdx
│ ├── 08-map-interface.mdx
│ ├── 09-hashmap.mdx
│ ├── 10-treemap.mdx
│ ├── 11-comparator-vs-comparable.mdx
│ ├── 12-queue-and-deque.mdx
│ ├── 13-priorityqueue.mdx
│ └── meta.json
│
├── 17-stream-api/
│ ├── 01-need-of-stream-api.mdx
│ ├── 02-for-each-method.mdx
│ ├── 03-stream-basics.mdx
│ ├── 04-stream-intermediate-operations.mdx
│ ├── 05-stream-terminal-operations.mdx
│ ├── 06-stream-parallelism.mdx
│ └── meta.json
│
├── 18-collection-internals/
│ ├── 01-hashmap-internals.mdx
│ ├── 02-concurrenthashmap.mdx
│ ├── 03-copyonwritearraylist.mdx
│ ├── 04-linkedhashmap.mdx
│ ├── 05-failfast-vs-failsafe.mdx
│ └── meta.json
│
├── 19-concurrency-advanced/
│ ├── 01-threadpool-executor.mdx
│ ├── 02-callable-and-future.mdx
│ ├── 03-scheduledexecutorservice.mdx
│ ├── 04-lock-framework.mdx
│ ├── 05-readwritelock.mdx
│ ├── 06-semaphores.mdx
│ ├── 07-countdownlatch.mdx
│ ├── 08-cyclicbarrier.mdx
│ ├── 09-phaser.mdx
│ ├── 10-atomic-variables.mdx
│ └── meta.json
│
├── 20-jvm-internals/
│ ├── 01-jvm-architecture.mdx
│ ├── 02-classloader.mdx
│ ├── 03-jit-compiler.mdx
│ ├── 04-garbage-collector-types.mdx
│ ├── 05-memory-leaks.mdx
│ ├── 06-jvm-performance-tuning.mdx
│ └── meta.json
│
├── 21-nio/
│ ├── 01-path-and-files.mdx
│ ├── 02-buffers-and-channels.mdx
│ ├── 03-selectors.mdx
│ ├── 04-asynchronous-io.mdx
│ └── meta.json
│
├── 22-modern-java/
│ ├── 01-optional-class.mdx
│ ├── 02-records.mdx
│ ├── 03-sealed-classes.mdx
│ ├── 04-switch-expressions.mdx
│ ├── 05-text-blocks.mdx
│ ├── 06-pattern-matching-instanceof.mdx
│ ├── 07-virtual-threads.mdx
│ └── meta.json
│
├── 23-file-handling/
│ ├── 01-file-reading-writing.mdx
│ ├── 02-buffered-io.mdx
│ ├── 03-serialization.mdx
│ ├── 04-deserialization.mdx
│ └── meta.json
│
├── 24-design-patterns/
│ ├── 01-singleton.mdx
│ ├── 02-factory.mdx
│ ├── 03-abstract-factory.mdx
│ ├── 04-builder.mdx
│ ├── 05-prototype.mdx
│ ├── 06-adapter.mdx
│ ├── 07-observer.mdx
│ ├── 08-strategy.mdx
│ ├── 09-decorator.mdx
│ └── meta.json
│
├── 25-testing/
│ ├── 01-junit-basics.mdx
│ ├── 02-mockito.mdx
│ ├── 03-test-driven-development.mdx
│ └── meta.json
│
├── 26-build-tools/
│ ├── 01-maven.mdx
│ ├── 02-gradle.mdx
│ └── meta.json
│
├── 27-spring-core/
│ ├── 01-ioc-container.mdx
│ ├── 02-beans.mdx
│ ├── 03-dependency-injection.mdx
│ ├── 04-spring-configurations.mdx
│ └── meta.json
│
├── 28-spring-boot/
│ ├── 01-spring-boot-intro.mdx
│ ├── 02-auto-configuration.mdx
│ ├── 03-rest-controller.mdx
│ ├── 04-crud-api.mdx
│ ├── 05-jpa-and-hibernate.mdx
│ └── meta.json
│
└── 29-rest-api/
├── 01-what-is-rest.mdx
├── 02-http-methods.mdx
├── 03-request-response.mdx
├── 04-status-codes.mdx
├── 05-rest-best-practices.mdx
└── meta.jsonWritten By: Shiva Srivastava
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