1. Java Types

In Java, data types are divided into two main categories: Primitive Types and Reference (Object) Types. Understanding these types is crucial for effective programming in Java.

1. Primitive Types

Primitive types are the basic data types provided by Java. They are not objects and hold their values directly in memory. Java has eight primitive data types:

Type	Size (in bytes)	Default Value	Description
byte	1	0	8-bit signed integer
short	2	0	16-bit signed integer
int	4	0	32-bit signed integer
long	8	0L	64-bit signed integer
float	4	0.0f	Single-precision 32-bit floating-point
double	8	0.0	Double-precision 64-bit floating-point
char	2	'\u0000'	Single 16-bit Unicode character
boolean	1 (not precisely defined)	false	Represents true or false values

public class PrimitiveExample {
    public static void main(String[] args) {
        int number = 10; // Integer
        char letter = 'A'; // Character
        boolean isActive = true; // Boolean
    }
}

2. Object (Reference) Types

Reference types, also known as object types, refer to objects and hold a reference to the memory location where the object is stored. They can be created from classes, interfaces, and arrays. Key characteristics include:

• Dynamic Size: The size of an object is determined at runtime.
• Null Reference: A reference type can be assigned a null value, indicating that it does not point to any object.

Common Object Types:

Type	Description
Classes	User-defined data types that encapsulate data and behavior.
Interfaces	Abstract types that define a contract for classes to implement.
Arrays	A collection of elements of the same type, stored in contiguous memory locations.

public class ObjectExample {
    public static void main(String[] args) {
        String text = "Hello, World!"; // String object
        Integer number = new Integer(10); // Integer object
        int[] numbers = {1, 2, 3, 4, 5}; // Array of integers
    }
}

3. Summary of Java Types

Type Category	Description	Examples
Primitive Types	Basic data types holding their values directly.	int, char, boolean
Reference Types	Hold references to objects in memory.	String, Array, Custom Class

4. Key Differences Between Primitive and Reference Types

Feature	Primitive Types	Reference Types
Storage	Directly stores values	Stores references to objects
Size	Fixed size (defined by type)	Dynamic size (depends on object)
Default Value	Has a default value	Default is null
Null Value	Cannot be null	Can be null