Java Programming Language: A Complete Guide to Learn

Java is an object-oriented programming language created by Sun Microsystems in 1995 and now maintained by Oracle. Its code runs on any operating system through the JVM (Java Virtual Machine), which consolidated it in corporate back-ends, Android apps, and banking systems.

• What is the Java programming language?
• Why learn Java in 2026?
• How to write your first program in Java?
• Basic concepts: variables, conditionals, and loops
• How does object orientation work in Java?
• Next steps: frameworks and advanced topics

What is the Java programming language?

The Java programming language is a high-level, object-oriented, statically typed language, created by Sun Microsystems (now part of Oracle) and released in 1995. The source code is compiled to bytecode, which the JVM (Java Virtual Machine) runs on any operating system — the "write once, run anywhere" principle.

This portability is Java's main competitive advantage: the same program runs on Windows, macOS, and Linux without changes, which made the language a default choice for long-lived enterprise software.

The Java platform evolves at a predictable pace. Since 2018, the JDK (Java Development Kit) follows a release cadence every six months, with LTS (Long-Term Support) versions every two years, according to the Oracle Java SE Support Roadmap. The most recent LTS version, Java 25, was released on September 16, 2025 with at least eight years of support, per Oracle's official announcement.

Why learn Java in 2026?

Java remains among the most used languages in the world: 29.4% of developers who responded to the Stack Overflow Developer Survey 2025 worked with Java in the past year, which places it as the 7th most popular programming language in the survey. This reach translates into open jobs, mature libraries, and a huge community for answering questions.

Java is also a strategic entry point: those who master its fundamentals migrate easily to Kotlin, C#, and other object-oriented languages. If you are still comparing options, see here at CodeCrush the 7 most used programming languages in the world and the detailed comparison between Java and Go.

How to write your first program in Java?

To write your first program in Java, install the official development kit, choose an editor, and run the traditional "Hello, World". The complete process takes less than thirty minutes:

1. Install the JDK: download the Java Development Kit from Oracle's site or use an OpenJDK distribution; it contains the javac compiler and the JVM.
2. Choose an IDE (Integrated Development Environment): IntelliJ IDEA and Eclipse are the most used options and have free versions.
3. Create a file called MeuPrimeiroPrograma.java and type the code below.
4. Compile and run through the IDE or the terminal, with javac MeuPrimeiroPrograma.java followed by java MeuPrimeiroPrograma.

public class MeuPrimeiroPrograma {
    public static void main(String[] args) {
        System.out.println("Olá, Mundo!");
    }
}

Every Java program starts with the main method: it is what the JVM looks for when running the class. System.out.println prints the text to the console.

Basic concepts: variables, conditionals, and loops

The first block of study in Java covers variables, conditional structures, and loops — the same programming logic fundamentals that apply to any language, but with Java's syntax and static typing.

Variable declaration and assignment

In Java, every variable has an explicitly declared type: int for integers, double for floating-point numbers, and String for text.

// Declaring variables of different types
int numero;
double valor;
String nome;

// Assigning values
numero = 10;
valor = 3.14;
nome = "Renata Weber";

The compiler prevents you from storing text in an int variable, for example — that is static typing catching errors even before the program runs.

Conditional structures (if-else)

int idade = 25;

if (idade >= 18) {
    System.out.println("Você é maior de idade.");
} else {
    System.out.println("Você é menor de idade.");
}

The if structure checks whether the age is greater than or equal to 18 and executes the block corresponding to the condition's result.

Loops (for)

for (int i = 1; i <= 5; i++) {
    System.out.println("Número: " + i);
}

The for loop counts from 1 to 5 and prints each number. It is the most common repetition structure in Java, alongside while and for-each for collections.

How does object orientation work in Java?

Object orientation in Java organizes the program into classes — molds that define attributes and behaviors — and objects, which are instances of those classes. The four pillars are classes/objects, inheritance, encapsulation, and polymorphism, and mastering them is what separates those who "write code" from those who design modular and reusable software.

Classes and objects

// Defining a class called "Carro"
class Carro {
    String marca;
    String modelo;
    int ano;

    // Method to display information about the car
    void exibirInformacoes() {
        System.out.println("Marca: " + marca);
        System.out.println("Modelo: " + modelo);
        System.out.println("Ano: " + ano);
    }
}

public class Main {
    public static void main(String[] args) {
        Carro meuCarro = new Carro();

        meuCarro.marca = "Toyota";
        meuCarro.modelo = "Corolla";
        meuCarro.ano = 2022;

        meuCarro.exibirInformacoes();
    }
}

The Carro class defines attributes and a method; the meuCarro object is a concrete instance with its own values.

Inheritance

// Base class "Animal"
class Animal {
    void fazerBarulho() {
        System.out.println("O animal faz algum som");
    }
}

// Derived class "Cachorro" that inherits from "Animal"
class Cachorro extends Animal {
    @Override
    void fazerBarulho() {
        System.out.println("O cachorro late!");
    }
}

public class Main {
    public static void main(String[] args) {
        Animal meuAnimal = new Cachorro();
        meuAnimal.fazerBarulho();
    }
}

The Cachorro class inherits from Animal with the extends keyword and overrides the fazerBarulho method — reusing structure without duplicating code.

Encapsulation

// Class "Pessoa" with private attributes
class Pessoa {
    private String nome;
    private int idade;

    public String getNome() {
        return nome;
    }

    public void setNome(String novoNome) {
        nome = novoNome;
    }

    public int getIdade() {
        return idade;
    }

    public void setIdade(int novaIdade) {
        idade = novaIdade;
    }
}

In encapsulation, attributes are private and can only be read or changed through public methods (get and set), protecting the object's internal state.

Polymorphism

class Computador {
    void ligar() {
        System.out.println("O computador está ligado.");
    }
}

class Notebook extends Computador {
    @Override
    void ligar() {
        System.out.println("O notebook está ligado.");
    }
}

public class Main {
    public static void main(String[] args) {
        Computador meuDispositivo = new Notebook();
        meuDispositivo.ligar();
    }
}

Polymorphism allows a reference of type Computador to execute the behavior of the derived class Notebook — the same method, with different results depending on the actual object.

Next steps: frameworks and advanced topics

After the fundamentals, the natural path in Java goes through three fronts. First, explore frameworks and libraries that accelerate professional development: Spring for web back-end and APIs, Hibernate for data persistence, and the Android SDK for mobile apps.

Second, practice deliberately: write small programs on your own and solve exercises on sites with programming challenges to consolidate syntax and reasoning.

Third, deepen advanced topics as you gain experience: concurrency and threads, network programming, collections and streams, and graphical interfaces. These topics appear frequently in interviews for mid-level and senior Java positions.

Conclusion

Learning the Java programming language continues to be one of the safest bets for those who want to make a living from software development: corporate demand is constant, the ecosystem is mature, and the LTS version cycle ensures that the investment in learning doesn't age quickly. Start with "Hello, World", advance with discipline through the pillars of object orientation, and only then move on to frameworks like Spring — constant practice, more than theory, is what turns a beginner into a competent Java developer.