Java Fundamentals Proyect

Repository dedicated to demonstrating technical mastery of Java (SE) fundamentals,
focusing on best practices, clean code, and performance.

Note

In this proyect, my objetive is to learn while i code until i dominate all the fundamentals of Java.
I have created milestones and issues for all the pending tasks in this repository.
I would appreciate any advice or recommendations on how to expand both my knowledge and my portfolio in this area.

Thanks in advance! 💖

01 | Basics

Essential concepts of Java

File	Content
Variables.java	Declaration, initialization, constants (final), casting, variable scope
DataTypes.java	Primitive types (byte, short, int, long, float, double, char, boolean) and String
Operators.java	Arithmetic, relational, logical, assignment, and ternary operators
ControlFlow.java	if/else, switch (classic and expression), for, for-each, while, do-while, break/continue
Arrays.java	One-dimensional arrays and matrices (2D), iteration, sorting, searching
Methods.java	Methods, parameters, overloading, recursion, varargs

02 | Object-Oriented Programming (OOP)

The pillars of OOP in Java, with independent and executable examples

File	Concept	Content
Classes.java	Classes and objects	Attributes, constructor, this, methods
Encapsulation.java	Encapsulation	Private attributes, getters/setters, internal state protection
Inheritance.java	Inheritance	extends, super, code reusability, @Override
Polymorphism.java	Polymorphism	Dynamic dispatch, superclass references pointing to subclasses
Interfaces.java	Interfaces	Contracts, multiple interfaces, default methods, lambdas
AbstractClasses.java	Abstract classes	Abstract vs. concrete methods, non-instantiable

03 | Collections (Java Collections Framework)

Standard data structures for storing and manipulating groups of objects

File	Content
ListsExample.java	ArrayList and LinkedList: add, insert, remove, iterate / traverse
SetsExample.java	HashSet (no duplicates, unordered) and TreeSet (sorted)
MapsExample.java	HashMap and TreeMap: key-value pairs, getOrDefault, iteration / traversal
ComparatorsExample.java	Comparable (natural ordering) vs. Comparator (external/custom ordering)

04 | Exception Handling

Managing runtime errors in a controlled manner

File	Content
ExceptionHandling.java	try/catch/finally, multiple catch blocks, common exceptions (ArithmeticException, NullPointerException, etc.)
CustomExceptions.java	Custom exceptions: checked (extends Exception) vs. unchecked (extends RuntimeException)
TryWithResources.java	Automatic resource management using try-with-resources and AutoCloseable

05 | Lambdas and Streams (Modern Java)

Functional programming (introduced in Java 8+), lambda expressions and the Streams API

File	Content
LambdasBasics.java	Functional interfaces: Function, BiFunction, Predicate, Supplier, Runnable, method references
StreamsBasics.java	filter, map, forEach, collect, count, anyMatch, allMatch
AdvancedStreams.java	reduce, groupingBy, sorted with Comparator, statistics, IntStream

06 | Algorithms

Clear and fully commented implementations of the algorithms that appear most often in classic programming problems

Sorting

File	Algorithm	Complexity
BubbleSort.java	Bubble Sort	O(n²)
QuickSort.java	Quick Sort (divide and conquer)	O(n log n) average
MergeSort.java	Merge Sort (stable)	O(n log n) guaranteed

Search

File	Algorithm	Complexity
BinarySearch.java	Binary Search (iterative and recursive)	O(log n)

Recursion

File	Algorithm	Complexity
Fibonacci.java	Fibonacci: recursive, memoized, and iterative	O(2ⁿ) / O(n) / O(n)
Factorial.java	Factorial: recursive and iterative	O(n)

Dynamic Programming

File	Algorithm	Complexity
Knapsack01.java	0/1 Knapsack Problem	O(n × capacity)
LongestCommonSubsequence.java	Longest Common Subsequence (LCS)	O(n × m)

Graphs

File	Algorithm	Complexity
BFS.java	Breadth-First Search (queue-based)	O(V + E)
DFS.java	Depth-First Search (recursive and iterative)	O(V + E)

Classic Algorithms

File	Algorithm	Description
FizzBuzz.java	FizzBuzz	The classic screening filter
PrimeNumbers.java	Prime Verification + Sieve of Eratosthenes	O(√n) and O(n log log n)
Palindrome.java	Palindrome Check (two pointers approach)	O(n)
ReverseString.java	Reverse a String (manual and recursive)	O(n)
TwoSum.java	Two Sum: brute force vs. HashMap	O(n²) vs. O(n)

꧁⎝ ON PROCESS 😄 ⎠꧂

Important

If someone has more ideas to expand my project I will apreciate it! :p
I’ll keep adding more things and learning as I continue working on this repository ^^