Rules for creating a class
=> Using class keyword to create a class.
public class Home
{
}
=> Give a class name meaningful (template).
=> Class name must start with Uppercase.
=> No special characters allowed except (_) underscore and ($) dollor symbol.
=> No space allowed inbetween class names.
Data types in java
Java data types define the type of data a variable can store in a program. They are categorized into two types
- Primitive data types
- Non primitive data types.
=> PRIMITIVE DATA TYPES : Store simple values directly in memory.It's categorized into two types Numeric and Non numeric type.
NUMERIC TYPE :
byte: 1 byte (8 bits). Range from -128 to 127. Used to save memory in large arrays.short: 2 bytes (16 bits). Range from -32,768 to 32,767. Used for moderate numbers where memory is tight.int: 4 bytes (32 bits). Range from -2.14 billion to 2.14 billion. This is the default type for whole numbers.long: 8 bytes (64 bits). Extremely wide numerical range.float: 4 bytes (32 bits). Sufficient for 6 to 7 decimal digits of precision.double: 8 bytes (64 bits). Provides up to 15 decimal digits of precision. This is the default type for decimal numbers in Java.
NON NUMERIC TYPE
char: 2 bytes (16 bits). Stores a single character enclosed in single quotes (e.g., char grade = 'A';).boolean: Stores only two possible values: true or false. Typically used for conditional flags and decision logic.
=> NON PRIMITIVE DATA TYPES: Store memory references to objects.
String: Represents an immutable sequence of characters enclosed in double quotes (e.g., String name = "Alice";).Arrays: Collections of multiple elements of the data type grouped under a single name (e.g., int[] scores = {90, 85, 88};).Classes: Custom user-defined blueprints that combine attributes (variables) and behaviors (methods) into unique entities.
Static variable :
=> In Java, when a variable is declared with the static keyword.
=> Then, a single variable is created and shared among all the objects at the class level.
=> Static variables are, essentially, global variables.
Key Characteristics :
Class-Level: We can create static variables at the class level only.
Accessed through Class Name: Static variables can be called directly with the help of a class only.
Single Copy: Every object of the class accesses and shares the exact same memory location.
Global Availability: Changes made to a static variable by one object are instantly visible to all other objects
public class Mobile
{
static int price = 23000;
static String name = "Vivo T5X 5g";
public static void main(String [] args){
System.out.println(Mobile.name);
System.out.println(Mobile.price);
}
}
OUTPUT :