https://github.com/natanzeraa/learning-java
Repository made to store and share my java learning. I am covering the very basics, intermediate and advanced level topics.
https://github.com/natanzeraa/learning-java
Last synced: 4 months ago
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Repository made to store and share my java learning. I am covering the very basics, intermediate and advanced level topics.
- Host: GitHub
- URL: https://github.com/natanzeraa/learning-java
- Owner: natanzeraa
- Created: 2024-10-07T14:45:21.000Z (8 months ago)
- Default Branch: main
- Last Pushed: 2024-10-22T14:39:46.000Z (8 months ago)
- Last Synced: 2024-12-27T07:34:46.475Z (5 months ago)
- Language: Java
- Size: 86.9 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
[//]: # ()
[//]: # ()
# Learning Java
*This repository is dedicated to the Java basics*
*We're covering:*
- Variables
- Data types
- Primitive and Non-primitive types
- Control structures
- Loops
- Arrays
- Classes
- Objects
- Inheritance
- Polymorphism
- Access Modifiers
[//]: # (---)
[//]: # (## Primitive Data Types)
[//]: # ()
[//]: # ( Data Type Size Description)
[//]: # ()
[//]: # ( byte 1 byte Stores whole numbers from -128 to 127)
[//]: # ( short 2 bytes Stores whole numbers from -32,768 to 32,767)
[//]: # ( int 4 bytes Stores whole numbers from -2,147,483,648 to 2,147,483,647)
[//]: # ( long 8 bytes Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)
[//]: # ( float 4 bytes Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits)
[//]: # ( double 8 bytes Stores fractional numbers. Sufficient for storing 15 decimal digits)
[//]: # ( boolean 1 bit Stores true or false values)
[//]: # ( char 2 bytes Stores a single character/letter or ASCII values)
[//]: # ()
[//]: # (---)
[//]: # ()
[//]: # (### Non-Primitive Data Types)
[//]: # ()
[//]: # (Non-primitive data types are called reference types because they refer to objects.)
[//]: # ()
[//]: # (The main difference between primitive and non-primitive data types are:)
[//]: # ()
[//]: # (Primitive types are predefined (already defined) in Java. Non-primitive types are created by the programmer and is not defined by Java (except for String).)
[//]: # (Non-primitive types can be used to call methods to perform certain operations, while primitive types cannot.)
[//]: # (A primitive type always has a value, while non-primitive types can be null.)
[//]: # (A primitive type starts with a lowercase letter, while non-primitive types starts with an uppercase letter.)
[//]: # (Examples of non-primitive types are Strings, Arrays, Classes, Interface, etc.)
[//]: # ()
[//]: # (---)
[//]: # (## Variables)
[//]: # ()
[//]: # (Variables are ways to store data in the program memory, so it can be manipulated in many ways.)
[//]: # ()
[//]: # (But first you need to "start" a variable in order to store some value. In Java you can do this by following this structure:)
[//]: # ()
[//]: # (**Type variableName = value;**)
[//]: # ()
[//]: # (**Example:**)
[//]: # ()
[//]: # ( String name = "Eliud Kipchoge";)
[//]: # ( char gender = 'M';)
[//]: # ( int age = 39;)
[//]: # ( float height = 1.77f;)
[//]: # ( double weight = 52.30d;)
[//]: # ( boolean isAnAthlete = true;)
[//]: # ( byte heartRate = 127;)
[//]: # ( short maratonSteps = 32767;)
[//]: # ( long centimetersRunned = 9223372036854775807L;)
[//]: # ()
[//]: # (You can see the variables file here: [Variables.java](https://github.com/natanzeraa/learning-java/blob/main/Variables.java))
[//]: # ()
[//]: # (---)
[//]: # (## Arrays)
[//]: # ()
[//]: # (Arrays are one of the most important and used data structure, if you have any contact with programming languages, it's quit impossible to not use a list, array or whatever the language you're learning calls it.)
[//]: # ()
[//]: # (Basically in Java, arrays are a way to store "a list of multiple elements" of the same type in a single variable.)
[//]: # ()
[//]: # (For example: imagine that you have a lottery app, and wants to store lucky numbers in it. The structure to do it is the following:)
[//]: # ()
[//]: # (**type[] arrayName = new type[intNumber];**)
[//]: # ()
[//]: # (1. Declare the type of the array (String, int, float, char, long, short, byte, etc...) and add the "[]" to indicate it is an array)
[//]: # (2. Give it a name, it can be whatever you want, since it follows the camel case rules ( likeThisOneRightHere ))
[//]: # (3. You need initialize the array by typing ( new type[intNumber] ), this is necessary to initialize and indicate how many elements will be stored in the array.)
[//]: # ()
[//]: # (**Example:**)
[//]: # ()
[//]: # ( int[] intArr = new int[3];)
[//]: # ( )
[//]: # (You can add elements to the java array by doing this:)
[//]: # ()
[//]: # ( intArr[0] = 5;)
[//]: # ( intArr[1] = 16;)
[//]: # ( intArr[2] = 87;)
[//]: # ()
[//]: # (1. Define the position of the element to be inserted ( intArr[0] ))
[//]: # (2. Give it a value respecting its type)
[//]: # ()
[//]: # (**Obs:** *In the above example we're using integers, and this type in java just like many other numeric types has a max limit that cannot be exceeded, for example integers can represent numbers from -2147483648 to 2147483647. But this is a topic to [Primitive and Non-Primitive](#types) types.*)
[//]: # ()
[//]: # (You can see the arrays file here: [Lists.java](https://github.com/natanzeraa/learning-java/blob/main/Lists.java))
[//]: # ()
[//]: # (---)
[//]: # ()
[//]: # (### Array List)
[//]: # ()
[//]: # (This is also an array but a little bit different way to work with.)
[//]: # (Basically Array Lists are dynamic arrays, you don't need to predefine its length.)
[//]: # ()
[//]: # (Every Array List is gonna store a certain type of elements, and it can be any type available in Java.)
[//]: # ()
[//]: # (You can add and remove as many elements as you want, and everything is ok!)
[//]: # ()
[//]: # (**Structure**)
[//]: # ()
[//]: # ( ArrayList variableName = new ArrayList();)
[//]: # ()
[//]: # (- Declare ArrayList type first)
[//]: # (- Than write what type of elements its gonna store)
[//]: # (- Declare the variable name)
[//]: # (- And initialize the array)
[//]: # ()
[//]: # (You can also initialize it with or without values in it.)
[//]: # ()
[//]: # (**Structure:**)
[//]: # ()
[//]: # ( ArrayList variableName = new ArrayList(Arrays.asList(values, separated, by, comma));)
[//]: # ()
[//]: # (- Do the same as the first one)
[//]: # (- Import Arrays from java.util.Arrays)
[//]: # (- Call the asList() method)
[//]: # (- Pass the values separating them by comma)
[//]: # ()
[//]: # (**Example:**)
[//]: # ()
[//]: # ( ArrayList brands = new ArrayList<>(Arrays.asList("Apple", "Microsoft", "Nvidia"));)
[//]: # ()
[//]: # (You can see the arrays file here: [Lists.java](https://github.com/natanzeraa/learning-java/blob/main/Lists.java))
[//]: # ()
[//]: # (---)
[//]: # ()
[//]: # (## Loops)
[//]: # ()
[//]: # (Loops are ways to iterate over a list of any type or even a certain amount of times given by an integer number.)
[//]: # ()
[//]: # (But first you might understand how it works and how to write it correctly:)
[//]: # ()
[//]: # (### For Loop)
[//]: # ()
[//]: # ( for (statement 1; statement 2; statement 3) {)
[//]: # ( // code here)
[//]: # ( })
[//]: # ()
[//]: # (- statement 1 sets the variable before the code starts)
[//]: # (- statement 2 defines a condition for the loop)
[//]: # (- statement 3 increases the variable set in the statement 1 every time the loop runs)
[//]: # ()
[//]: # (**Example:**)
[//]: # ( )
[//]: # ( int age = 26;)
[//]: # ( for(var i = 0; i < age; i++){)
[//]: # ( System.out.println(i);)
[//]: # ( })
[//]: # ()
[//]: # (### While Loop)
[//]: # ()
[//]: # ( while (statement) {)
[//]: # ( // code here)
[//]: # ( })
[//]: # ()
[//]: # (- statement defines a condition for the loop)
[//]: # ()
[//]: # (**Example:**)
[//]: # ( )
[//]: # ( int y = 0;)
[//]: # ( int x = 10;)
[//]: # ( )
[//]: # ( while(y < x) {)
[//]: # ( System.out.println(y++);)
[//]: # ( })
[//]: # ()
[//]: # (### Do While Loop)
[//]: # ()
[//]: # ( do {)
[//]: # ( // code here)
[//]: # ( } while(statement);)
[//]: # ()
[//]: # (- do block defines where the code block to be executed)
[//]: # (- statement defines a condition for the loop)
[//]: # ()
[//]: # (**Example:**)
[//]: # ()
[//]: # (int a = 0;)
[//]: # (int b = 10;)
[//]: # ()
[//]: # ( do {)
[//]: # ( System.out.println(a++);)
[//]: # ( } while(a < b);)
[//]: # ()
[//]: # ()
[//]: # (You can see the loops file here: [Loops.java](https://github.com/natanzeraa/learning-java/blob/main/Loops.java))
[//]: # ()
[//]: # (---)
[//]: # ()
[//]: # ()
[//]: # ()
[//]: # (---)
[//]: # ()
[//]: # (## Methods)
[//]: # ()
[//]: # (*Methods, are a block of code that only runs when it is called,*)
[//]: # (*they accept external data also known as parameters.*)
[//]: # (*Some languages can call methods as functions, because can execute certain actions.*)
[//]: # ()
[//]: # (**Example:**)
[//]: # ()
[//]: # ( public String showSomeText() {)
[//]: # ( return "This is a text";)
[//]: # ( })
[//]: # ()
[//]: # (*The code above is a method that returns a text.* )
[//]: # (*As you can see it does not take any parameters*)
[//]: # ()
[//]: # (*Now lets see a method that actually takes parameters.*)
[//]: # ()
[//]: # (**Example:**)
[//]: # ()
[//]: # ( public int sumOfTwoValues(int a, int b) {)
[//]: # ( return a + b;)
[//]: # ( })
[//]: # ()
[//]: # (*As you can see, this method is receiving two parameters and executing a sum of the two values.*)
[//]: # ()
[//]: # (*But now you must be asking yourself: How do I make this work? How do I use it?*)
[//]: # ()
[//]: # (*To use this method correctly, take a look at this example:*)
[//]: # ()
[//]: # ( public class Methods {)
[//]: # ( public static String someMethod(String argument) {)
[//]: # ( return argument;)
[//]: # ( })
[//]: # ( )
[//]: # ( public static void main(String[] args) {)
[//]: # ( String argument = someMethod("This is an argument!");)
[//]: # ( System.out.println(argument);)
[//]: # ( })
[//]: # ( })
[//]: # ()
[//]: # (**Example II:**)
[//]: # ( )
[//]: # ( public class Methods {)
[//]: # ( public static void main(String[] args) {)
[//]: # ( Sum sum = new Sum();)
[//]: # ( sum.sumOfTwoValues(10, 35);)
[//]: # ( })
[//]: # ( })
[//]: # ()
[//]: # ( class Sum {)
[//]: # ( public int sumOfTwoValues(int a, int b) {)
[//]: # ( return a + b;)
[//]: # ( })
[//]: # ( })
[//]: # ()
[//]: # (You can see the methods file here: [Methods.java](https://github.com/natanzeraa/learning-java/blob/main/Methods.java))
[//]: # ()
[//]: # (---)