Introduction to Classes, Objects and Methods

• Essence of Java: Class is the basis of object-oriented programming in Java.
• Class Definition: Defines the nature of an object, including data and methods.
• Importance of Classes: Understanding classes, objects and methods is crucial to writing sophisticated programs.

Fundamentals of Classes

• Object Model: A class specifies data and the code that will operate on it.
• Class Instances: Objects are instances of a class.
• Class Members: Methods and variables that make up a class are called class members.
• Instance Variables: Also known as data members.

General Form of a Class

• Class Structure: Defined using the class keyword.
• Declaration of Variables and Methods:

class NomeDaClasse {
    tipo var1;
    tipo var2;
    // ...
    tipo varN;
    tipo método1(parâmetros) {
        // corpo do método
    }
    tipo método2(parâmetros) {
        // corpo do método
    }
    // ...
    tipo métodoN(parâmetros) {
        // corpo do método
    }
}

• Logical Entity: A class must group logically connected information.

Defining a Class

• Example Class: Vehicle that encapsulates information about vehicles.
• Instance Variables: passengers, fuelcap, mpg.

class Vehicle {
    int passengers; // número de passageiros
    int fuelcap; // capacidade de armazenamento de combustível em galões
    int mpg; // consumo de combustível em milhas por galão
}

• Object Creation:

Vehicle minivan = new Vehicle(); // cria um objeto Vehicle chamado minivan

• Access to Instance Variables: Using the dot operator (.)

minivan.fuelcap = 16;

Complete Example
Program that uses the Vehicle class (not included in the snippet).
See Vehicle.java

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