Java Programming

The online doc A good textbook: Introduction to Java Programming and Data Structures, Author Y. Daniel Liang

👉 Introduction

What is Java?

object oriented programming lannguage
create by James Gosling in 1995
similar to c++ but easier
3 billion devices run Java programs
very popular

What can you build with Java

Mobile apps for Android (Kotlin is more common or Swift)
Desktop App using Java Swing, JavaFX
Enterprise Applications
Games (such as Minecraft)
Cloud based applications
Web applications

Java Usages

Build enterprise application
learn more

Compiled Vs Interpreted language

Difference between Compiler and Interpreter in Java
A compiler is a special program that processes statements written in a particular programming language and turns them into machine language or "code" that computer's processor uses.
The interpreter read each stateemnt of code and then converts or executes it directly

Static vs Dynamic Type Checking

The process of verifying and enforcing the constraints of types - type checking - may occur either at compile time (static check) or at a run-time (dynamic check)
Static type checking is when types are checked during compilation, before the program is run. This means that any type errors will be caught early on and can be fixed before the program is deployed. Dynamic type checking, on the other hand, happens at runtime. This means that type errors can go undetected until the program is actually being used.

🚩 Environement setup (Intellij IDEA)

Go to the offical website of Jetbrains
If you are a student, you can get InteliJ IDEA free.
To download Intellij IDEA, go to developer tools > Pluging and services > Toolbox App
Then open toolbox and download IntelliJ IDEA

🚩 Getting Started

First Java Program

Compiling and Running via Terminal

View bytecode

read more on bytecode here

Public static void main

👉 The basics

The example codes for the following subjects can be found here

Reverse keywords
Comments
- two ways to add comments
- use "//" (single ligne comments) or "/" and "/" (Multi Line comments)
- Comments has no effect when you run a code
Variables - A varibles allows us to store a value into a placeholer which we can use it later
Primitives Data Types Differences
- Primitives types are used to store simple values. For instance, whole numbers, decimal values and characters:
  - boolean
  - byte
  - short
  - char
  - int
  - long
  - float (store decimal value, but bigger number and take more space in memory)
  - double
Numeric Literals with underscore
- Reprensent big numbers with underscore for readability

Arithmetic operarors
Increment and Decrement Operators
Comparison Operators
Short and re-assignment
Naming Variables
- CamelCase
Strings
- String API Documentation
Reference types and objects

Reference types and objects differences

Pass by Value differences
- pass by value
Arrays
- data structure that allows to store multiple values in one variable
O and null Values for arrays

👉 Loops

code snipet can be found here

loops - constraint that allows us to repeat a block of codes

For loops
Loops and arrays
Enhanced For loop
For i vs Enhanced For loop
While loop
Do while

👉 'if' Stateements

code snipet can be found here

if statement allows us to execute a block of codes based on a condition

if statement
if statement with conditions
Else if
AND logical operator
OR logical operator
logical operators recap
- a review of the chapter logic in discrete math or discrete structure or math for computer science can help
- a recommended course for discrete math

Switch

Use switch to replace nested if conditions

👉 Packages

👉 Access modifiers

All you need to know can be found here

👉 Methods

When building method:
- Access modifiers
- Optional static
- Return type
- Name
- Optional parameters
- Method Body
- Optional return value

Exammple: public static void main(String[] args) { body }

Naming convention for methods
- Methods should be verbs, in mixed case with the first letter lowercase, with the first letter of each internal word capitalized
- e.g: run(); runFast(); getBackground();

👉 Beyond the basics

Understand public static void main

Type inferance with var

It allows to define a variable using var and without specifying the type of it

public class Main {
// private var brand = "jpstayfocus" (var cant work)
public static void main(String[] args) {
    // Type inference with var keyword (works for every datatype,
    // but can be used only for local variables)

    /*
    String name = "Jamila";
    String[] names = {"Jamila", "Joseph"};
    int age = 22;
    boolean isAdult = false;
    double balance = 1_000_000.33;
    */

    var name = "Jamila";
    var names = new String[]{"Jamila", "Joseph"};
    var age = 22;
    var isAdult = false;
    var balance = 1_000_000.33;
}
}

Break keyword and loops
Continue keyword
Final keyword
- allows to create constants, prevent inheritance, and method overriding
Implicit and Explicit type casting

👉 Strings

Working with strings
How strings are stored in memory
Strings are immutable
String lateral vs String Onject
Comparing String with ==
Comparing String with .equals
Useful String Static Methods

👉 Dates

Code on Dates can be found here

Local Date Time
Local Date and Local Time
Creating specific Dates
Zoneelds
Other Dates Classes
- Difference between insant and localdateTime

👉 Big decimal

Problem with double (precision)
Big decimal
Big decimal methods

Exception in java

Exception in java explained here
Exception Hierarchy

Working with files

Creating Files
Writing to Files
Reading from files
Try with Ressources

jpstayfocus / java-basic-and-beyond