Understanding Variables

Variables are containers for storing data values. In Java, every variable must be declared with a specific data type, which tells the computer what kind of data the variable will hold.

Common Data Types

• int: Stores whole numbers, like 7 or -42.
• double: Stores decimal numbers, like 3.14 or -0.01.
• boolean: Stores true or false values.
• char: Stores single characters, like 'A' or 'z'.
• String: Stores sequences of characters, like "Hello, Java!".

Declaring and Using Variables

To declare a variable, write the data type, then the variable name, and assign a value with =:

int age = 16;
double price = 9.99;
boolean isStudent = true;
char grade = 'A';
String name = "Alex";

Changing Values

You can change a variable's value at any time:

age = 17;
price = price - 2.00;

Why Variables Matter

Variables let programs remember information and perform calculations. They're the building blocks for everything in programming!

Real-World Analogy

Imagine variables as labeled jars in a kitchen. Each jar (variable) can hold a specific kind of ingredient (data type).

Common Mistakes

• Forgetting to declare the data type.
• Trying to store a string in an int variable.