Java Basics Quiz

Test your Java skills! This quiz checks if you’re ready for FRC programming.

Each question shows the answer immediately so you can learn as you go.

Question 1: Variables

What does this code print?

int score = 10;
score = score + 5;
System.out.println(score);

Show Answer

Answer: 15

Why?

First line: score is set to 10.
Second line: score + 5 = 15, then score = 15
Third line: Prints 15.

Think of it like:

You have a box labeled “score”.
Put 10 in the box.
Add 5 more to the box.
Now the box has 15.

Question 2: Strings

What does this code print?

String name = "FRC";
String greeting = "Hello " + name;
System.out.println(greeting);

Show Answer

Answer: Hello FRC

Why?

+ joins strings together (called concatenation)
"Hello " + "FRC" = "Hello FRC"

Think of it like:

Glue two pieces of paper together.
One says “Hello ”, the other says “FRC”.
After gluing: “Hello FRC”.

Question 3: If Statements

What does this code print?

int speed = 7;
if (speed > 5) {
    System.out.println("Fast!");
} else {
    System.out.println("Slow");
}

Show Answer

Answer: Fast!

Why?

speed is 7
7 > 5 is true.
Run the code inside if
Skip the code inside else

Think of it like:

“Is the speed greater than 5?”.
Yes! Print “Fast!”.
No need to check the “else” part.

Question 4: If-Else If

What does this code print?

int score = 85;
if (score >= 90) {
    System.out.println("A");
} else if (score >= 80) {
    System.out.println("B");
} else {
    System.out.println("C");
}

Show Answer

Answer: B

Why?

score is 85
85 >= 90? No, skip first block.
85 >= 80? Yes! Print “B”.
Skip the else block.

Think of it like:

Check conditions in order.
Stop at the first one that’s true.
Don’t check the rest.

Question 5: Loops

How many times does this print?

for (int i = 0; i < 3; i++) {
    System.out.println("Hello");
}

Show Answer

Answer: 3 times

Why?

i = 0: Print (i is 0, 0 < 3)
i = 1: Print (i is 1, 1 < 3)
i = 2: Print (i is 2, 2 < 3)
i = 3: Stop (i is 3, 3 < 3 is false)

Think of it like:

Count: 0, 1, 2.
That’s 3 numbers.
Print 3 times

Question 6: While Loops

What does this code print?

int count = 3;
while (count > 0) {
    System.out.println(count);
    count = count - 1;
}

Show Answer

Answer:

3
2
1

Why?

count = 3: 3 > 0? Yes, print 3, then count becomes 2.
count = 2: 2 > 0? Yes, print 2, then count becomes 1.
count = 1: 1 > 0? Yes, print 1, then count becomes 0.
count = 0: 0 > 0? No, stop.

Think of it like:

Keep going while the condition is true.
Stop when it becomes false.

Question 7: Methods

What does this code print?

public int add(int a, int b) {
    return a + b;
}

// Somewhere else:
int result = add(3, 4);
System.out.println(result);

Show Answer

Answer: 7

Why?

Call add(3, 4)
a = 3, b = 4
return 3 + 4 = 7.
result = 7
Print 7

Think of it like:

A method is a recipe.
Give it ingredients (3 and 4)
It cooks them together (adds them)
Gives you the result (7)

Question 8: Boolean Logic

What does this code print?

boolean hasPermission = true;
boolean isAdmin = false;
if (hasPermission && isAdmin) {
    System.out.println("Access granted");
} else {
    System.out.println("Access denied");
}

Show Answer

Answer: Access denied

Why?

hasPermission is true.
isAdmin is false.
true && false = false.
Run the else block.

Think of it like:

&& means “both must be true”.
One is false, so the whole thing is false.
Like saying “I have a ticket AND I’m VIP”.
If you don’t have VIP, you can’t get in.

Question 9: Arrays

What does this code print?

int[] scores = {10, 20, 30};
System.out.println(scores[1]);

Show Answer

Answer: 20

Why?

Arrays start at index 0.
scores[0] = 10.
scores[1] = 20.
scores[2] = 30.

Think of it like:

Mailboxes on a street.
Address 0 has mail (10)
Address 1 has mail (20)
Address 2 has mail (30)
You check address 1: you get 20.

Question 10: Objects

What does this code print?

public class Robot {
    public String name;

    public Robot(String robotName) {
        name = robotName;
    }
}

Robot myRobot = new Robot("MARS");
System.out.println(myRobot.name);

Show Answer

Answer: MARS

Why?

Create a new Robot with name “MARS”.
Constructor sets name = "MARS"
Access myRobot.name
Print “MARS”

Think of it like:

A class is a blueprint for a house.
An object is the actual house built from the blueprint.
You can build many houses from one blueprint.
Each house can have different features.

Question 11: Null

What happens with this code?

String name = null;
System.out.println(name.length());

Show Answer

Answer: NullPointerException (crashes!)

Why?

name is null (nothing)
Can’t call methods on nothing.
Java throws an error.

How to fix:

String name = null;
if (name != null) {
    System.out.println(name.length());
}

Think of it like:

Trying to open a door that doesn’t exist.
You can’t do it!
Check if the door exists first.

Question 12: Increment

What does this code print?

int count = 5;
count++;
System.out.println(count);

Show Answer

Answer: 6

Why?

count++ means “add 1 to count”.
Same as count = count + 1
5 + 1 = 6

Think of it like:

A shortcut for adding 1.
programmers are lazy!
++ is shorter than + 1

Question 13: Modulo

What does this code print?

int x = 10 % 3;
System.out.println(x);

Show Answer

Answer: 1

Why?

% is the modulo operator (remainder)
10 ÷ 3 = 3 with remainder 1.
So 10 % 3 = 1

Think of it like:

You have 10 cookies.
Divide into groups of 3.
You get 3 groups (9 cookies)
1 cookie left over.
That’s the remainder!

Question 14: Equality

What does this code print?

String a = new String("hello");
String b = new String("hello");
if (a == b) {
    System.out.println("Same");
} else {
    System.out.println("Different");
}

Show Answer

Answer: Different

Why?

== checks if they’re the SAME object.
.equals() checks if they have the SAME VALUE.
a and b are different objects with same value.

How to fix:

if (a.equals(b)) {
    System.out.println("Same");  // This prints!
}

Think of it like:

Two different cookies.
Both are chocolate chip.
They’re not the SAME cookie.
But they’re the same TYPE of cookie.

Question 15: Scope

What does this code print?

int x = 5;
if (true) {
    int x = 10;  // Line A
    System.out.println(x);  // Line B
}
System.out.println(x);  // Line C

Show Answer

Answer: This code doesn’t compile!

Why?

Can’t declare x twice in the same scope.
The outer x is still visible inside the if.
Java doesn’t know which x you mean.

Fix:

int x = 5;
if (true) {
    x = 10;  // Just assign, don't redeclare
}
System.out.println(x);  // Prints 10

Think of it like:

You can’t have two people with the same name in the same room.
But you can have different people with same name in different rooms.

Scoring

Count your correct answers:

13-15 correct: 🌟 Amazing! You’re ready for advanced FRC programming!
10-12 correct: 👍 Great job! You understand most Java basics.
7-9 correct: 👌 Good start! Review the questions you missed.
Below 7: 📚 Keep learning! Try the Beginner Learning Path.

What to Learn Next

If you got 13-15 correct:

→ Ready for Intermediate Learning Path
→ Learn about FRC Programming
→ Build your first Robot Command

If you got 7-12 correct:

→ Review Java Basics
→ Practice more Examples
→ Try the Beginner Learning Path

If you got below 7:

→ Start with Beginner Learning Path
→ Learn Java from Scratch
→ Ask questions in our community

Practice More

Write your own code:

Make a calculator that adds two numbers.
Write a program that counts to 10.
Create a method that finds the larger of two numbers.
Build an array of your favorite foods.

Test yourself:

// Challenge 1: Make this print "Hello World" 5 times
// Your code here

// Challenge 2: Make a method that returns true if a number is even
// Your code here

// Challenge 3: Find the largest number in this array: {5, 2, 9, 1, 7}
// Your code here

Remember: Programming is a skill. Keep practicing and you’ll get better!

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