Java Variables – What They Are and How to Use Them

In Java, variables are like containers that store data values. You can think of them as placeholders for different types of data that your program can use.

🧑‍💻 Types of Java Variables

Java offers a variety of variable types, each designed to store specific kinds of data. Let’s go over them:

• String: Stores text (e.g., "Hello"). Strings are wrapped in double quotes.

• int: Stores whole numbers without decimals (e.g., 123 or -123).

• float: Stores numbers with decimals (e.g., 19.99 or -19.99).

• char: Stores a single character (e.g., 'a' or 'B'). Characters are wrapped in single quotes.

• boolean: Stores one of two possible values: true or false.

📄 Declaring (Creating) Variables

To create a variable, you need to define its type and assign it a value. Here’s the syntax:

type variableName = value;

For example:

java

String name = "John"; System.out.println(name);

This creates a variable name of type String and assigns it the value "John". The println() method then prints it to the screen.

➡️ Working with Numbers

To store numbers, you can create an int variable like this:

java

int myNum = 15; System.out.println(myNum);

This creates a variable myNum of type int and assigns it the value 15.

You can also declare the variable without assigning a value immediately, like this:

java

int myNum; myNum = 15; System.out.println(myNum);

If you change the value of an existing variable, it overwrites the previous value:

java

int myNum = 15; myNum = 20; // myNum is now 20 System.out.println(myNum);

🔒 Final Variables – Making Them Constant

If you don’t want to allow changes to a variable after it’s been assigned a value, you can declare it as final. This means the value becomes immutable (unchangeable).

java

final int myNum = 15; myNum = 20; // will generate an error: cannot assign a value to a final variable

The final keyword ensures the variable’s value cannot be altered.

🧳 Other Variable Types

Here’s how you can declare variables of other types:

• int: int myNum = 5;

• float: float myFloatNum = 5.99f;

• char: char myLetter = 'D';

• boolean: boolean myBool = true;

• String: String myText = "Hello";

📍 Summary Box

Variable Type	Description	Example
String	Stores text	String name = "John";
int	Stores whole numbers	int myNum = 15;
float	Stores numbers with decimals	float myFloatNum = 5.99f;
char	Stores a single character	char myLetter = 'D';
boolean	Stores true or false values	boolean myBool = true;

🚀 Next Steps

Now that you've learned about Java variables, you're ready to explore more! Next up:

• Java Data Types

• Java Operators

• Java Strings

• Java Conditional Statements

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