Time to explore 2 - Data Type Examples 😎
📊 Examples with Numbers and Strings
In this lesson, we’ll learn about different data types in Java — these are the kinds of values your robot can use, like numbers, letters, and words. Each type has its own special rules and powers. Let’s check them out!
🔢 Integers (int
)
Integers are whole numbers. That means they don’t have decimals. You can use them to count things, measure scores, or store positions.
int score = 10;
int lives = 3;
Java automatically uses integer math when you’re working with just int
numbers.
Operation | Code | What It Does | Result |
---|---|---|---|
Addition | int sum = 5 + 2; | 5 plus 2 | 7 |
Subtraction | int diff = 5 - 2; | 5 minus 2 | 3 |
Multiplication | int product = 5 * 2; | 5 times 2 | 10 |
Division | int quotient = 5 / 2; | 5 divided by 2, decimal gets cut off | 2 |
Remainder | int rem = 5 % 2; | What’s left after dividing 5 by 2 | 1 |
📝 Note: If you divide
5 / 2
usingint
, you don’t get 2.5 — Java chops off the decimal and gives just2
.
🧮 Decimal Numbers (double
)
A double
can store decimal numbers like 2.5
or 3.14
. It’s great for when you need precise values, like distances or percentages.
double speed = 2.5;
double batteryLevel = 75.5;
Operation | Code | What It Does | Result |
---|---|---|---|
Multiplication | double r = 4.5 * 1.2; | 4.5 times 1.2 | 5.4 |
Order of Ops | double r = 4.5 * 1.2 + 3; | Multiply first, then add | 8.4 |
Division | double d = 5.0 / 2.0; | Divides with decimals | 2.5 |
✅ Reminder: To get a decimal answer, at least one number must have a
.0
in it! If both numbers areint
, you’ll get anint
result.
🔤 Characters (char
)
A char
(short for character) stores a single letter or symbol. It’s surrounded by single quotes like 'A'
or '%'
.
char grade = 'A';
char symbol = '!';
Operation | Code | What It Does | Result |
---|---|---|---|
Assign letter | char letter = 'A'; | Stores letter A | 'A' |
Next letter | char next = (char)(letter + 1); | Adds 1 to A (ASCII code) = B | 'B' |
Symbol | char symbol = '!'; | Stores exclamation mark | '!' |
💡 Fun Fact: Letters are secretly stored as numbers (ASCII).
'A'
is65
,'B'
is66
, and so on!
🧵 Strings
A String
is a bunch of characters stuck together — like a word or sentence. You use double quotes for strings: "Hello"
String name = "Robo";
String message = "Hello, world!";
Operation | Code | What It Does | Result |
---|---|---|---|
Basic join | "Hello" + " World" | Joins the two parts together | ”Hello World” |
Add variable | "Hello, " + name | Adds the value inside name | ”Hello, Robo” |
Add number to string | "Score: " + 10 | Turns 10 into text, then joins it | ”Score: 10” |
Multi-line | "Line1\nLine2" | \n makes a new line | Line1 (newline) Line2 |
💡 Tip: Strings aren’t just text — they’re objects that have cool powers like
.length()
(how long it is) and.toUpperCase()
(shouty version!)
🧠 Summary Table
Data Type | What It’s For | Examples | Notes |
---|---|---|---|
int | Whole numbers | 5 + 2 , 10 / 3 , 7 % 4 | No decimals, does regular math |
double | Decimal numbers | 5.0 / 2.0 , 3.14 * 2 , 1.5 + 3 | Gives accurate decimal answers |
char | Single characters | 'A' , 'Z' , '!' , '1' | Must use single quotes ' ' , ASCII aware |
String | Words and sentences | "Hello" + name , "Score: " + 5 | Double quotes, use + to build messages |
🧪 Challenge: Try printing out these different types using
System.out.println()
and see what happens!
System.out.println(5 + 2); // int math
System.out.println(5.0 / 2.0); // double math
System.out.println('A' + 1); // adds to char, prints number!
System.out.println("Hi " + "there!"); // String join
➡️ 🤖 Minigame!
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