How to learn a programming languages

Step 1 : Data types, Variables, Constants, Identifiers, Literals

Step 2: Operators , Expression

Step 3: Statements

A variable and a constant are temporary storage locations in RAM. The key difference between them is that a variable's value can be changed, while a constant's value remains fixed.

Variables and constants are stored in RAM because they can be accessed quickly and easily by the CPU.

Data types

1. Basic Data types (Java Primitive data types - #8)

   

   Fixed-point numbers are used to ensure 100% accuracy of a number's value. In contrast, using float or double types can lead to slight variations in the value across different systems due to differences in CPU architecture.

   For example, Computer A might represent a number as 1.589, while Computer B could represent it as 1.59, and Computer C as 1.58900000.

   These variations occur because different systems handle floating-point numbers differently based on their CPU architecture.

   To ensure 100% accuracy, we use fixed-point numbers, especially in critical applications like banking systems or POS systems, where precision is essential.

   Primitive Data Types

   • Boolean - 1bit (true and false)

   ---

   Signed integers ( - to + )

   • byte - 8 bits (1 byte)
   • short - 16 bits (2 bytes)
   • int - 32 bits (4 bytes)
   • long - 64 bits (8 bytes)

   ---

   • float - 32 bits (4 bytes)
   • double - 64 bits (8 bytes)

   ---

   Unsigned integer (+ only)

   • char - 16 bits (2 bytes) - unsigned integera

   Type inference, sometimes called type reconstruction, refers to the automatic detection of the type of an expression in a formal language.

   example : Python

            Java 11 to up version has this feature (implicitly check) 
   

   How to declare a variable in java with syntax

   identifier [= value]{, identifier[=value]}

   var identifier = value {,identifier = value}

   

How to declared variable in Java

int x = 10; // already data type declared - implicit

var x = 5> 2; // Boolean

var x = 20+2; //int

var = 30.5; //double

• We cant use keywords (void, main etc.), boolean literals (true, false) or null literal (null) as a identifier
• When declaring an identifier, it can't start with a digit. It should always begin with a java letter, for example: N5ame.
• Identifiers can't start with symbols, except for the underscore (_) and dollar sign ($).
• Literal mean a source code representation of a data type , But in Java literal is the source code representation of a value of a primitive type the String type or the null type.