Przegląd Języka Java

Study Notes

Java Language Overview

Java is a high-level, object-oriented programming language.
Designed to have "write once, run anywhere" (WORA) portability.
Compiled into bytecode (.class files).
Bytecode is executed by the Java Virtual Machine (JVM) and is platform independent.
Java is widely used in web applications, mobile apps (Android), enterprise applications, and more.
Key features include:
- Object-oriented programming principles (encapsulation, inheritance, polymorphism)
- Strong typing system
- Automatic garbage collection
- Exception handling mechanisms
- Rich standard library

Java Data Types

Java uses primitive data types to represent fundamental values:
- int: 32-bit integer
- long: 64-bit integer
- float: 32-bit single-precision floating-point number
- double: 64-bit double-precision floating-point number
- char: 16-bit Unicode character
- boolean: true or false logical value
- byte: 8-bit integer
- short: 16-bit integer
Java also has reference data types (objects).
Objects can store complex data and methods in their respective class definitions.

Java Object-Oriented Concepts

Classes: Blueprints for creating objects.
Objects: Instances of classes.
Methods: Functions associated with classes or objects.
Variables: Data associated with classes or objects.

Variables and Data Types

Variables store data values.
Variable declaration syntax: dataType variableName;
- Example: int age;
Variable initialization: dataType variableName = value;
- Example: int age = 30;
Data types define the type of data a variable can hold.
Primitive data types (e.g. int, float, boolean) directly store values.
Reference data types (e.g. objects) store references to objects.

Control Structures

if-else statements: Conditional execution of code.
switch statements: Selection between multiple cases.
for loops: Iterating over a range of values.
while loops: Repeating a block of code as long as a condition is true.
do-while loops: Repeating a block of code at least once, then continuing as long as a condition is true.

Java Operators

Arithmetic operators: +, -, *, /, %.
Comparison operators: ==, !=, >, <, >=, <=.
Logical operators: && (AND), || (OR), ! (NOT).
Assignment operators: =, +=, -=, *=, /=, %=

Java Input/Output (I/O)

Java provides classes for reading input from the console and writing output to the console.
Scanner class reads input from the user.
System.out.println() prints output to the console.
System.in is the standard input stream.

Exception Handling

Java uses exceptions to handle errors that may occur during program execution.
try-catch blocks are used to handle exceptions.
throws keyword declares that a method might throw an exception.
finally block is executed regardless of whether an exception occurs.

Arrays in Java

Arrays are used to store collections of values of the same data type in a contiguous memory location.
Declaration: dataType[] arrayName = new dataType[size]; or dataType arrayName[] = new dataType[size];
Access elements of an array using their index.

Classes and Objects

Creating classes:
- Define data members (attributes/variables) and methods (behaviors).
- Example: a Dog class with attributes like name and breed and method to bark().
Creating objects:
- Using the class name to create an instance of that class.
Accessing class members (methods, attributes): using dot notation.
Constructors: initializing objects upon their creation.

Methods

Methods are operations that objects can perform.
Return types (e.g., int, String) determine the data type of the value returned.
Methods can take arguments.
void methods don't return any value.

Inheritance and Polymorphism

Inheritance allows classes to inherit properties and methods from other classes.
- Enables code reusability and establishes relationships between classes.
Polymorphism allows methods to have different behaviors depending on the object they are called upon.

Packages

Organize Java classes into logical units and prevent naming conflicts.

Libraries and Frameworks

Libraries provide ready-made functions and components for specific tasks.
Frameworks offer infrastructure for building certain types of applications, like web applications.

Commonly used libraries in Java

The Java Standard Library (e.g., java.util, java.lang) provides core functionalities.
External libraries like Apache libraries are extensively used for projects ranging from data handling to HTTP programming.

Description

Wszystko o języku programowania Java: jego cechy, zasady programowania obiektowego oraz różne typy danych. Dowiedz się, jak Java zapewnia przenośność i wydajność dzięki maszynie wirtualnej. To quiz, który pomoże ci zgłębić podstawy języka Java oraz jego zastosowania w różnych dziedzinach.