Java Classes and Objects Flashcards

Object-Oriented Programming (OOP)

• Emphasizes the use of objects which contain data and methods.
• Key components include attributes, behaviors, and class structures.

Attributes and Behavior

• Attributes are characteristics of an object, such as color.
• Behavior refers to actions defined by the object type.

Class Fundamentals

• A class is a blueprint for creating objects.
• Class definition begins with public class ClassName {.

Methods

• Methods represent behaviors; they encapsulate operations for an object.
• Example method syntax:

  static void sayHello() {
      System.out.println("Hello World!");
  }
  

Code Reuse

• Methods can be written once and reused multiple times, enhancing efficiency.

Return Values

• Methods can return values using syntax like:

  static int sum(int a, int b) {
      return a + b;
  }
  

• Return type must match the data type of the returned value.

Access Modifiers

• Public allows class accessibility from any class.
• Default (no modifier) grants access within the same package.
• Protected extends access to subclasses.
• Private restricts access to the defining class only.

Getters and Setters

• Getters retrieve values, syntax example:

  public String getVariable() {
      return variable;
  }
  

• Setters assign values, syntax example:

  public void setVariable(String value) {
      this.variable = value;
  }
  

Encapsulation

• Combines data (variables) and methods into a single unit to improve data security.

Constructors

• Special methods for initializing objects.
• Constructors must have the same name as the class and no return type.

Primitive Data Types

• Includes byte, short, int, long, float, double, boolean, char.

Boolean Data Type

• Represents true or false values.

Reference Variables

• Created when instantiating an object from a class.

Math Class Operations

• Predefined methods for mathematical calculations, such as:
  • Math.abs(): Absolute value
  • Math.ceil(): Rounds up to the nearest integer
  • Math.max() and Math.min(): Returns the maximum or minimum of parameters
  • Math.pow(): Raises a number to a specified power

Special Mathematical Functions

• sqrt(): Computes the square root.
• sin() and cos(): Compute sine and cosine, respectively.

Final Keyword

• Declares constants that cannot be modified after initial assignment. Example:

  public static final double PI = 3.14;
  

Packages

• A package groups related classes and can contain sub-packages for organizing code.