GitHub Wiki - Yash-777/LearnJava GitHub Wiki

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โœ… Yes, ๐Ÿ’ก Idea, ๐Ÿ” search ๐Ÿ“š Summary ๐Ÿงช Sample ๐Ÿ”‘ Key, ๐Ÿ” Author/Secure ๐Ÿ“ฆ Package, ๐Ÿงพ Full JavaDoc, โš™๏ธ Setting / .java file, ๐Ÿ›  Refactored

Tables

Single line code

Code Information
String s = "Yash"; String literal

๐Ÿ’ก A blank/empty line that contains only whitespace (such as tabs or spaces) inside a <pre> block can cause formatting or rendering issues, like:

  • Collapsed formatting
  • Misaligned indentation
  • Extra spacing or unexpected behavior in GitHub Wiki
Header 1 Header 2 
public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, world!");
    }
}
      
public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }
}
Stream Stream in Detail oracle article 
List transactionsIds = 
    transactions.stream()
                .filter(t -> t.getType() == Transaction.GROCERY)
                .sorted(comparing(Transaction::getValue).reversed())
                .map(Transaction::getId)
                .collect(toList());
 image

Task lists

- [x] #739
- [ ] Add delight to the experience when all tasks are complete ๐ŸŽ‰
  • #739
  • Add delight to the experience when all tasks are complete ๐ŸŽ‰

Using emojis

@octocat :+1: This PR looks great - it's ready to merge! :shipit:

@octocat ๐Ÿ‘ This PR looks great - it's ready to merge! :shipit:

Alerts

Header 1 Header 2 
> [!NOTE]
> Useful information that users should know, even when skimming content.

Note

Useful information that users should know, even when skimming content.

 
> [!TIP]
> Helpful advice for doing things better or more easily.

Tip

Helpful advice for doing things better or more easily.

 
> [!IMPORTANT]
> Key information users need to know to achieve their goal.

Important

Key information users need to know to achieve their goal.

 
> [!WARNING]
> Urgent info that needs immediate user attention to avoid problems.

Warning

Urgent info that needs immediate user attention to avoid problems.

 
> [!CAUTION]
> Advises about risks or negative outcomes of certain actions.

Caution

Advises about risks or negative outcomes of certain actions.

Example Collapsible Content

A collapsible section with markdown

Click to expand!

Heading

  1. A numbered
  2. list
    • With some
    • Sub bullets

NB: Make sure you have an empty line after the closing tag, otherwise the markdown/code blocks won't show correctly.

Click to expand! 
function logSometing(something) {
   console.log(`Logging: ${something}`);
}
Click to close! - Already open... 
function logSometing(something) {
   console.log(`Logging: ${something}`);
}

Show Some Code then Expand

Click to see more:
Given the following python code 
from pychartjs import BaseChart

class myChart(BaseChart):
    pass
chartJSON = myChart().get()
Write the following HTML
<div class="container">
   <canvas id="myChart"></canvas>
</div>
... and JS
var data = {{ chartJSON | safe }}
var ctx = document.getElementById("myChart").getContext('2d');
var myChart = new Chart(ctx, data);

In a class-based object-oriented language, in general, state is carried by instances, methods are carried by classes, and inheritance is only of structure and behavior. Basic, Refactoring Techniques

Method signature: It consists of method name and parameter list (number/type/order of the parameters). methodName(parametersList y). An instance method in a subclass with the same signature and return type as an instance method in the super-class overrides the super-class's method.

Java OOP concepts
Class  - Collection of a common features of a group of object [static/instance Fields, blocks and Methods]
Object - Instance of a class (instance fields)
Abstraction - Process of hiding complex info and providing required info like API, Marker Interfaces ...
Encapsulation(Security) - Class Binding up with data members(fields) and member functions.
Inheritance  (Reusability by placing common code in single class)
 1. Multilevel - {A -> B -> C} 2. Multiple - Diamond problem {A <- (B) -> C} [Java not supports] 3. Cyclic {A <-> B} [Java not supports]
 * Is-A   Relation - Class A extends B
 * Hash-A Relation - Class A { B obj = new B(); } - (Composition/Aggregation)
Polymorphism (Flexibility) 1. Compile-Time Overloading    2. Runtime Overriding  [Greek - "many forms"]


int[] arr = {1,2,3}; int arrLength = arr.length;   // Fixed length of sequential blocks to hold same data type
String str = "Yash"; int strLength = str.length(); // Immutable Object value can't be changed.

List<?> collections = new ArrayList<String>(); int collectionGroupSize = collections.size();
Map<?, ?> mapEntry = new HashMap<String, String>();
Set<?> keySet = mapEntry.keySet(); // Set of Key's
Set<?> entrySet = mapEntry.entrySet(); // Set of Entries [Key, Value]

// Immutable Objects once created they can't be modified. final class Integer/String/Employee
Integer val = Integer.valueOf("100"); String str2 = String.valueOf(100); // Immutable classes
final class Employee { // All Wrapper classes, java.util.UUID, java.io.File ...
    private final String empName; // Field as Final(values can be assigned only once) Only getter functions.
    public Employee(String name) { this.empName = name; }
}

Native Java Code for Hashtable.h, Hashtable.cpp SQL API.

You can check your current JDK and JRE versions on your command prompt respectively,

  • JDK javac -version [C:\Program Files\Java\jdk1.8.0_121\bin] o/p: javac 1.8.0_121
  • JRE java -version [C:\Program Files\Java\jdk1.8.0_121\bin] o/P: java version "1.8.0_102"

JAVA_HOME - Must be set to JDK otherwise maven projects leads to compilation error. [ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK? C:\Softwares\OpenJDK\, 7-zip

Fatal error compiling: invalid target release: JRE and JDK must be of same version 1.8.0.XXX

Disable TLS 1.0 and 1.1security-libs/javax.net.ssl: TLS 1.0 and 1.1 are versions of the TLS protocol that are no longer considered secure and have been superseded by more secure and modern versions (TLS 1.2 and 1.3).

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