Primitive Data Types and Variables

What is a Variable? A variable is a container that holds a value. In Java, every variable must have a specific data type, which tells the compiler how much memory to reserve for it and what kind of data it can store.

Statically-Typed Language: Java is a statically-typed language. This means you must declare the type of a variable before you can use it, and the type cannot be changed later. This helps catch errors early, during compilation, rather than at runtime.

The 8 Primitive Types: Java has eight fundamental data types, known as primitive types. They are the most basic building blocks for data.

• Integer Types: For whole numbers.

• byte: 8-bit. Range: -128 to 127. Use for saving memory in large arrays.

• short: 16-bit. Range: -32,768 to 32,767. Also for memory saving.

• int: 32-bit. Range: -2.1 billion to 2.1 billion. The most commonly used integer type.

• long: 64-bit. For very large whole numbers. Must be appended with an L (e.g., long bigNumber = 3000000000L;).

• Floating-Point Types: For numbers with fractional parts.

• float: 32-bit. For single-precision decimals. Must be appended with an f (e.g., float pi = 3.14f;).

• double: 64-bit. For double-precision decimals. The default and most common type for decimal numbers.

• Other Types:

• boolean: Represents true or false values. Used for logical conditions.

• char: 16-bit Unicode character. Can hold a single character, enclosed in single quotes (e.g., char grade = 'A';).

Declaration and Initialization:

• Declaration: int myAge; (Reserves memory for an integer named myAge).

• Initialization: myAge = 30; (Assigns a value to the variable).

• Combined: int myAge = 30; (Declares and initializes in one step).

Mini-Exercise: Declare and initialize a variable for each of the 8 primitive types. Print each variable to the console to see its value.

int score = 100;
double price = 19.99;
char initial = 'J';
boolean isLoggedIn = false;
long worldPopulation = 7800000000L;

System.out.println("Score: " + score);
System.out.println("Logged In: " + isLoggedIn);