Fundamentals of the Java Language and its Syntax

Java: A robust and versatile programming language, widely used in various applications. Developed by James Gosling at Sun Microsystems (currently Oracle), its popularity is due to portability, safety and ease of use. This guide explores the fundamental concepts of Java language, including syntax, patterns and practical examples.

Main Characteristics of Java

• Independent Platform: The Java Virtual Machine (JVM) allows the execution of Java programs in any installed JVM system.
• Object Oriented (POO): Based on the principles of POO, promoting modularity and code reuse.
• Security: Robust safety mechanisms protect data and prevent vulnerabilities.
• Multithreading: Supports simultaneous execution of multiple threads.
• Garbage Collection: Automatic memory management, simplifying development.

Basic structure of a Java program

A Basic Java Program consists of classes and methods. See a simple example:

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

Code Description

public class HelloWorld: declares a class called HelloWorld. In Java, every code lies within a class.

public static void main(String[] args): Program input point. The main method is executed when starting the program.

System.out.println("Olá, Mundo!"): Print "Hello, world!" on the console.

data types and variables

Java is a strongly typed language. Each variable needs to have a definite type. Main types of data:

<code>Tipo     Tamanho   Valores Possíveis

byte     8 bits    -128 a 127

short    16 bits   -32.768 a 32.767

int      32 bits   -2.147.483.648 a 2.147.483.647

long     64 bits   -9.223.372.036.854.775.808 a 9.223.372.036.854.775.807

float    32 bits    Precisão simples

double   64 bits    Precisão dupla

char     16 bits    Um caractere Unicode

boolean  1 bit      true ou false</code>

Example of variable declaration

public class TiposDeDados {
    public static void main(String[] args) {
        int idade = 25;
        double salario = 4500.50;
        char inicial = 'J';
        boolean empregado = true;

        System.out.println("Idade: " + idade);
        System.out.println("Salário: " + salario);
        System.out.println("Inicial do nome: " + inicial);
        System.out.println("Empregado: " + empregado);
    }
}

Flow Control

Java offers flow control structures such as if, else, for, while and switch.

Example: conditional structures

public class ControleDeFluxo {
    public static void main(String[] args) {
        int numero = 10;

        if (numero > 0) {
            System.out.println("O número é positivo.");
        } else if (numero < 0) {
            System.out.println("O número é negativo.");
        } else {
            System.out.println("O número é zero.");
        }
    }
}

Example: Repetition bond

public class LacosDeRepeticao {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Contador: " + i);
        }

        int contador = 5;
        while (contador > 0) {
            System.out.println("Contador: " + contador);
            contador--;
        }
    }
}

Object Odurated Programming (POO) in Java

POO is fundamental in Java. Key Concepts:

1. Class: Model for creating objects.
2. Object: Instance of a class.
3. Encapsulation: Control of access to class data.
4. inheritance: one class inherits attributes and methods of another.
5. Polymorphism: A method behaves differently in subclasses.

Example: Class and Object

class Pessoa {
    String nome;
    int idade;

    void apresentar() {
        System.out.println("Olá, meu nome é " + nome + " e tenho " + idade + " anos.");
    }
}

public class OrientacaoObjetos {
    public static void main(String[] args) {
        Pessoa pessoa = new Pessoa();
        pessoa.nome = "João";
        pessoa.idade = 30;
        pessoa.apresentar();
    }
}

Conclusion

Java is a powerful language for developing various applications. This guide presented the basic foundations. Explore libraries and tools to deepen your knowledge.

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