Every variable in Java must have a data type that determines what values it can hold and operations that can be performed on it. Java has two categories of data types: primitive and reference. Primitive types represent basic values like integers and characters, while reference types refer to objects. Some examples of primitive data types are int for integers, float for floating point numbers, and char for characters.

1. Every variable must have a data type. A variable's data type determines the values that
the variable can contain and the operations that can be performed on it. The Java
programming language has two categories of data types: primitive and reference.
Primitives are data types whose state represents a number, a character, or a true/false
indication.
Primitive types are not class types; they do not provide any behavior associated with the
type appropriate values they hold. Java has eight primitive types that should look
familiar to you from other languages: The table below lists some examples of primitive
data types.
int Integer 32-bit two’s 178
complement
float Single-precision floating 32-bit IEEE 754
point
char A single character 16-bit Unicode ‘c ’
character
boolean A boolean value (true or true or false true
false)
false
Reference types in Java are Classes, Interfaces, and Arrays. When you declare a
reference type variable you are specifying that the variable will refer, or point to an
object, instead of holding a single value as a primitive type.
Here's an example of declaring an integer variable:
int maxLoginAttempts = 3;

2. When you create a variable in Java, you must know a few things:
• You must know what data type you are going to use.
• You must know what you want to call the variable.
• You might also want to know the value with which the variable should be
initialized.