basics of java. part 1.

***** _What is Java?****_
Java is a popular programming language, created in 1995.It is owned by Oracle, and more than 3 billion devices run Java.
It is used for:

1. Mobile applications (specially Android apps)
2. Desktop applications
3. Web applications
4. Web servers and application servers Games 5.Database connection

Java Syntax
public class Main {
public static void main(String[] args) {
System.out.println("Hello World");
}
}

Java Comments
*Single-line comments start with two forward slashes (//).
Any text between // and the end of the line is ignored by Java (will not be executed).

Multi-line comments start with / and ends with */.

_Java Variables_
In Java, there are different types of variables, for example:

1. String - stores text, such as "Hello". String values are surrounded by double quotes.
   2_. int_ - stores integers (whole numbers), without decimals, such as 123 or -123.

2. float - stores floating point numbers, with decimals, such as 19.99 or -19.99.

4._ char_ - stores single characters, such as 'a' or 'B'. Char
values are surrounded by single quotes.

1. boolean - stores values with two states: true or false.

**_Declaring (Creating) Variables: syntax :-

type variableName = value;

Java Data Types
Data types are divided into two groups:

Primitive data types - includes byte, short, int, long, float, double, boolean and char.

Non-primitive data types - such as String, Arrays and Classes.

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.

Java Type Casting
Type casting is when you assign a value of one primitive data type to another type.

In Java, there are two types of casting:

1.Widening Casting (automatically) - converting a smaller type to a larger type size
byte -> short -> char -> int -> long -> float -> double

2.Narrowing Casting (manually) - converting a larger type to a smaller size type
double -> float -> long -> int -> char -> short -> byte

5_. boolean -** stores values with two states: true or false.