Java Data Types

#java #webdev

Java Data Types
As explained in the previous chapter, a variable in Java must be a specified data type:

Example:

int myNum = 5; // Integer (whole number)
float myFloatNum = 5.99f; // Floating poin

t number
char myLetter = 'D'; // Character
boolean myBool = true; // Boolean
String myText = "Hello"; // String

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 (you will learn more about these in a later chapter)

Primitive Data Types

primitive data type specifies the type of a variable and the kind of values it can hold.

There are eight primitive data types in Java:

Data Type Description
byte Stores whole numbers from -128 to 127
short Stores whole numbers from -32,768 to 32,767
int Stores whole numbers from -2,147,483,648 to 2,147,483,647
long Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
float Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits
double Stores fractional numbers. Sufficient for storing 15 to 16 decimal digits
boolean Stores true or false values
char Stores a single character/letter or ASCII values

Non-Primitive (Reference) Data Types:

These data types are not predefined by the language and are created by the programmer (except for String). They store references to objects rather than the actual values. Examples include:
Classes: User-defined types that serve as blueprints for creating objects (e.g., String, Scanner, custom classes like Person).
Interfaces: Blueprints of a class, defining a set of methods that a class must implement.
Arrays: Used to store multiple values of the same data type in a single

Key Differences

Storage:
Primitive types store values directly on the stack, while non-primitive types store references to objects on the heap.
Default Values:
Primitive types have default values (e.g., 0 for int, false for boolean), while non-primitive types have a default value of null.
Methods:
Non-primitive types can have methods associated with them, allowing for operations on the data they represent, whereas primitive types do not.
Case Convention:
Primitive types start with a lowercase letter, while non-primitive types (classes, interfaces) typically start with an uppercase letter.