What are the differences between the main data types in Java?

In Java, the main data types are divided into primitive and reference types.

Primitive types include:

• byte (8 bits)
• short (16 bits)
• int (32 bits)
• long (64 bits)
• float (32-bit floating point)
• double (64-bit floating point)
• char (16-bit Unicode character)
• boolean (true or false)

The differences between them are in memory size, value range, and purpose. Primitives are stored directly in memory, while reference types (objects) contain references to data in the heap.

Example:

int a = 10; // primitive type
String s = "Hello"; // reference type