Java Write Once, Run Anywhere.

W.O.R.A. = Write Once, Run Anywhere

This is achieved by the JVM (Java Virtual Machine).

Every program must have a Class Java starts execution from main method statements end with semicolons ;

  
class MyClass
{
  public static void main(String[ ] args) {
  
    System.out.println("Hello world!");
  }
}

 /** This is a documentation comment */

/**********************

This is the start of a method

***********************/

Java arithmetic operators:

+ addition
- subtraction
* multiplication
/ division
% modulo

Operators

Any of the following comparison operators may be used to form the condition:

< less than
> greater than
!= not equal to
== equal to
<= less than or equal to
>= greater than or equal to

VOID

When you do not need to return any value from your method, use the keyword void. Notice the void keyword in the definition of the main method
this means that main does not return anything.

Use an ArrayList when you need rapid access to your data.
Use a LinkedList when you need to make a large number of inserts and/or deletes.

Arrays and Lists store elements as ordered collections, with each element given an integer index.
HashMap (like a php associative array) is used for storing data collections as key and value pairs. One object is used as a key (index) to another object (the value).
The put, remove, and get methods are used to add, delete, and access values in the HashMap.

RESTful API Design

For designing REST API endpoint we recommend 13 Best Practices to Make Your Users Happy.

Learn the basics of HTTP applied to REST
Don’t return plain text
Avoid using verbs in URIs
Use plural resource nouns
Return error details in the response body
Pay attention to status codes
Use status codes consistently
Don’t nest resources
Handle trailing slashes gracefully
Make use of the querystring for filtering and pagination
Learn the difference between 401 Unauthorized and 403 Forbidden
Make good use of 202 Accepted
Use a web framework specialised in REST APIs

Trivia:

Java Performance Puzzlers by Douglas Hawkins
Java Garbage Collection
[Dependency Injection Made Simple with Java Examples Clean Code and Best Practices](https://www.youtube.com/watch?v=GATSXm7WAxU)

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Java Write Once, Run Anywhere