In Java, every variable must have a specified data type. This determines the kind of values the variable can hold.
Example:
int age = 25; // Integer (whole number) float height = 5.75f; // Floating-point number char initial = 'A'; // Character boolean isStudent = true; // Boolean String greeting = "Hello"; // String
Types of Data Types
Data types in Java are divided into two main categories:
- Primitive Data Types
- Non-Primitive Data Types
Primitive Data Types
Primitive data types specify the type of a variable and the kind of values it can hold. Java has eight primitive data types:
| 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 Data Types
Non-primitive data types include classes, arrays, and interfaces. For now, we’ll focus on one common non-primitive type: String.
Example:
String city = "Manila";
Examples of Using Data Types
In this example, we declare different types of variables and print their values using the println() method.
int temperature = 28; // Integer
double pi = 3.14159; // Double
char grade = 'B'; // Character
boolean isJavaFun = true; // Boolean
String country = "Philippines"; // String
System.out.println("Temperature: " + temperature);
System.out.println("Pi: " + pi);
System.out.println("Grade: " + grade);
System.out.println("Is Java fun? " + isJavaFun);
System.out.println("Country: " + country);