Java Variables and Data Types | Hassan Bukhari

Java Notes

03 Java Fundamentals | Variables and Data types in Java | By Dummy for Dummies

Java Beginner Guide Variables Data Types

VARIABLES

Monkey loves bananas. Monkey collects bananas. But monkey can collect and deal with only a limited number of bananas. To collect and utilize more bananas, Monkey needs pockets or bags. If Monkey finds a bag, it will put all the bananas inside.

But wait, bananas are not the only thing Monkey likes. Monkey also likes mangoes and apples. So Monkey finds 2 more bags. Now Monkey has each bag for each fruit. And each bag has different sections where it can put the fruits one by one.

The Analogy

🐵 Monkey = You (the programmer)

🍎 Fruits = Information (numbers, words, etc.)

👜 Bags = Variables (where you store the info)

Now, why do you even need bags? Because sometimes you deal with numbers like 2 + 2, easy stuff. But sometimes you will face a monster number like:

Number

1234567890123456789

Imagine writing that everywhere in your code again and again. Painful, right? Instead, you just give it a name like number or simply n. Now, whenever you use n in your program, Java will treat it as 1234567890123456789. Easy, clean, and way more powerful when data grows big.

TYPES OF VARIABLES

Monkey was smart. Monkey put each fruit in a separate bag. You are smarter, you put each type of information in different variables as well. The different types or classes of variables are called "Data Types"

Consider you have 3 types of data/information:

Integer → 123

Decimal → 12.002

Word → "Coding"

Each type of data has its own class/type in Java:

123 → Integer (whole number)

12.002 → Double or Float (decimal numbers)

"Coding" → String (words, text)

Common Data Types in Java

Data Type	Description	Example
`int`	Stores whole numbers	`123`, `-99`
`double`	Stores decimal numbers (precise)	`3.14159`
`float`	Stores decimals (less precise, saves memory)	`2.5f`
`char`	Stores a single character	`'A'`, `'x'`
`String`	Stores text (capital S)	`"Hello 123"`
`boolean`	Stores true or false	`true`, `false`
`long`	Stores very big whole numbers	`123456789L`
`short`	Stores smaller whole numbers	`123`
`byte`	Even smaller whole numbers (efficiency)	`12`

THINGS TO REMEMBER

All datatype names are lower case except String, in which first letter is capital
String must be enclosed in double quotes like "Word"
char must be enclosed in single quote like 'A'
char can store just a single character 'L' or '@'
boolean values are both in lowercase i.e. true or false
Variable names must start with a small letter and can only contain letters, numbers, or underscore _
Each line of code in Java ends with a semicolon ;

CREATING VARIABLE INSIDE CODE

When creating a variable inside a code you need to first write its datatype, then a name for it, then assign it to a value. Let's store the word Skibidi in a variable.

It is a word so Datatype will be String
Name can be anything but must start with a small letter
Use equality = to assign the value
Then write the value "Skibidi"
After end of each line of code in java write semi colon ;

Java

public class Main {
    public static void main(String[] args) {
        String name = "Skibidi";
        System.out.println(name);  // This will print Skibidi
    }
}

Console Output

Skibidi

CREATING ALL IN ONE CODE

Java

public class VariablesExample {
    public static void main(String[] args) {
        int bananas = 123;
        double price = 12.002;
        String hobby = "Coding";
        char grade = 'A';
        boolean isHappy = true;

        System.out.println(bananas);  // This will print 123
        System.out.println(price);    // This will print 12.002
        System.out.println(hobby);    // This will print Coding
        System.out.println(grade);    // This will print A
        System.out.println(isHappy);  // This will print true
    }
}

Console Output

123 12.002 Coding A true

EXTRA TIPS

Declaration vs Initialization
If you just create a variable and do not assign any value, it is called "Declaration"
int num;

When you assign it a value later, it is called "Initialization"
num = 199;

CLOSING

That's it for Variables and Data types! In the next blog, Monkey won't just store fruits, Monkey will start playing with them 🍌➕🍎 (yes, I'm talking about operations and expressions).

Search This Blog

Hassan Codes