Java Mastery
Master Java from fundamentals to advanced concurrency and DSA templates. 11 phases covering everything you need for top tech company interviews.
Your Progress
Complete all 11 phases to master this track
Complete Java mastery roadmap — 11 phases from Java fundamentals to advanced concurrency, generics, and DSA templates for coding interviews.
Phase 1: Java Foundations
Master Java fundamentals: variables, data types, operators, control flow, and methods. The language foundation for all DSA coding.
What is Java?
Understand Java's philosophy, write-once-run-anywhere, and its role in Amazon's tech stack.
JDK, JRE, JVM
Understand the Java ecosystem: JDK, JRE, JVM, and how Java code executes.
Compilation and Execution
Understand how Java source code becomes bytecode and runs on the JVM.
Variables
Declare, initialize, and use variables in Java effectively.
Primitive Data Types
Master Java's 8 primitive types: byte, short, int, long, float, double, char, boolean.
Reference Types
Understand objects, arrays, and references vs primitives.
Type Casting
Master widening, narrowing, and explicit type casting in Java.
Operators
Master arithmetic, relational, logical, bitwise, and assignment operators.
Input and Output
Read user input with Scanner and print output with System.out.
if / else / switch
Master conditional logic with if, else if, else, and switch statements.
Loops
Master for, while, do-while loops, break, continue, and nested loops.
Methods
Define, call, overload methods. Understand parameters, return values, and pass-by-value.
Recursion in Java
Implement recursive solutions in Java with proper base cases and stack understanding.
Phase 2: Java Arrays & Strings
Master Java arrays, strings, and StringBuilder for efficient data manipulation in DSA problems.
Arrays in Java
Declare, initialize, traverse, and manipulate arrays in Java.
Multidimensional Arrays
Work with 2D arrays and matrices in Java.
Arrays Utility Class
Use Arrays.sort(), Arrays.copyOf(), Arrays.fill(), and other utility methods.
Strings in Java
Understand String creation, methods, and character operations.
String Immutability
Understand why Strings are immutable and how the String pool works.
StringBuilder
Use StringBuilder for efficient string concatenation in loops and algorithms.
String Methods
Master essential String methods: charAt, substring, indexOf, split, toCharArray, and more.
Phase 3: Java OOP
Master object-oriented programming in Java: classes, inheritance, polymorphism, and SOLID principles.
Classes and Objects
Define classes, create objects, and understand instance variables and methods.
Constructors
Master default, parameterized, and copy constructors.
this and static
Understand the this keyword and static variables/methods.
Encapsulation
Use access modifiers, getters, and setters for data hiding.
Inheritance
Extend classes, use super, and understand the IS-A relationship.
Polymorphism
Master compile-time and runtime polymorphism through overloading and overriding.
Abstraction
Use abstract classes and interfaces to define contracts.
Interfaces
Define and implement interfaces, default methods, and multiple inheritance.
Composition & SOLID
Prefer composition over inheritance. Understand SOLID principles.
Phase 4: Java Exceptions
Master exception handling in Java for robust, interview-ready code.
Exception Handling
Understand the exception hierarchy, try-catch-finally, and throw/throws.
Checked vs Unchecked Exceptions
Know the difference and when to use each type.
Custom Exceptions
Create your own exception classes for domain-specific error handling.
Phase 5: Java Collections
Master the Collections Framework — the most critical Java knowledge for DSA interviews.
Collections Overview
Understand the Collections Framework hierarchy: List, Set, Map, Queue.
ArrayList
Use ArrayList for dynamic arrays. Understand internal resizing and time complexities.
LinkedList
Use LinkedList for efficient insertions/deletions. Know when to use it vs ArrayList.
HashMap
Master HashMap for O(1) lookups. Understand hashing, collisions, and internal structure.
TreeMap & LinkedHashMap
Use TreeMap for sorted keys and LinkedHashMap for insertion order.
HashSet & TreeSet
Use HashSet for O(1) membership and TreeSet for sorted unique elements.
PriorityQueue (Heap)
Use PriorityQueue for min-heap and max-heap operations in DSA.
Deque & Stack
Use ArrayDeque for stack/queue operations and understand the Stack class.
Collections Utility Class
Use Collections.sort(), reverse(), shuffle(), and other utility methods.
Comparable & Comparator
Define natural ordering with Comparable and custom ordering with Comparator.
Choosing the Right Collection
Decision framework for selecting the correct collection for any DSA problem.
Phase 6: Java Generics
Write type-safe, reusable code with Java generics — essential for collections and DSA templates.
Phase 7: Java 8+ Features
Master modern Java features used in real-world code and interviews: lambdas, streams, and Optional.
Lambda Expressions
Write concise anonymous functions with lambda expressions.
Functional Interfaces
Use Predicate, Function, Consumer, Supplier for functional programming.
Stream API
Process collections with map, filter, reduce, sorted, and collect operations.
Optional
Handle null values elegantly with Optional.
Phase 8: Java Memory & JVM
Understand how Java manages memory — critical for debugging and interview questions.
Stack vs Heap
Understand where variables, objects, and references live in memory.
Garbage Collection
Understand how the JVM reclaims memory and when objects become eligible.
equals() and hashCode()
Override equals and hashCode correctly for HashMap and HashSet usage.
Java Pass-by-Value
Understand why Java is always pass-by-value and how references work.
Phase 9: Java Multithreading
Understand Java concurrency basics for interview questions and real-world code.
Threads and Runnable
Create threads with Thread class and Runnable interface.
Synchronization
Use synchronized keyword and locks to prevent race conditions.
ExecutorService & Futures
Use thread pools, Callable, and Future for concurrent task execution.
Phase 10: Java DSA Templates
Practical Java code templates for every DSA pattern — the ultimate coding interview toolkit.
Phase 11: Java Interview Mastery
Common Java interview questions, output prediction, debugging, and design decisions.