Which collection interface in Java does not allow duplicate elements?
Anonymous Quiz
15%
List
70%
Set
7%
Map
7%
Queue
What is a key difference between arrow functions and regular functions regarding 'this'?
Anonymous Quiz
22%
Arrow functions get their own 'this' bound at call time, just like regular functions
69%
Arrow functions don't have their own 'this'; they inherit it lexically from the surrounding scope
3%
Regular functions never have access to 'this'
6%
There is no meaningful difference
Topic: Java
🔍 Quick look before the question:
🔍 Quick look before the question:
public class Test {
static int counter = 0;
static synchronized void increment() {
counter++;
}
public static void main(String[] args) throws InterruptedException {
Thread t1 = new Thread(() -> {
for (int i = 0; i < 1000; i++) increment();
});
Thread t2 = new Thread(() -> {
for (int i = 0; i < 1000; i++) increment();
});
t1.start(); t2.start();
t1.join(); t2.join();
System.out.println(counter);
}
}
What will counter reliably print, and why?
Anonymous Quiz
35%
Some unpredictable number less than 2000, because of a race condition
35%
Exactly 2000, since synchronized serializes the increments
18%
Exactly 1000, because only one thread actually runs
12%
0, because static fields can't be modified by threads
What does the SQL DISTINCT keyword do?
Anonymous Quiz
7%
Sorts results
83%
Removes duplicate rows
3%
Groups rows
7%
Filters null values
What does Array.prototype.map() return?
Anonymous Quiz
18%
The same array modified in place
68%
A new array with transformed elements
8%
A single combined value
5%
Undefined
Topic: Debugging & Code Output
🔍 Quick look before the question:
🔍 Quick look before the question:
for i in range(5):
if i == 3:
continue
print(i)
Topic: SQL
🔍 Quick look before the question:
🔍 Quick look before the question:
BEGIN TRANSACTION;
UPDATE accounts SET balance = balance - 200 WHERE id = 1;
UPDATE accounts SET balance = balance + 200 WHERE id = 2;
COMMIT;
Why is wrapping both UPDATEs in a single transaction important here?
Anonymous Quiz
13%
It makes the two statements run faster
87%
It ensures both updates succeed or both roll back together
0%
It only matters for SELECT statements
0%
It has no functional effect, just style
Topic: Debugging & Code Output
🔍 Quick look before the question:
🔍 Quick look before the question:
def outer():
result = []
for i in range(3):
def inner():
return i
result.append(inner)
return [f() for f in result]
print(outer())
What does this print?
Anonymous Quiz
40%
[0, 1, 2]
35%
[2, 2, 2]
5%
[0, 0, 0]
20%
This raises a NameError
Which isolation level allows a transaction to read data another concurrent transaction has written but not yet committed?
Anonymous Quiz
15%
Serializable
17%
Repeatable Read
19%
Read Committed
49%
Read Uncommitted
What is the practical difference between Object.is(NaN, NaN) and NaN === NaN?
Anonymous Quiz
5%
Both return false
0%
Both return true
89%
Object.is returns true, === returns false, because === treats NaN as never equal to itself
5%
Object.is throws an error for NaN
Which of these creates a shallow copy of a list in Python?
Anonymous Quiz
0%
list2 = list1
63%
list2 = list1.copy()
26%
list2 = list1[:]
11%
Both B and C
What is a primary key's main purpose in a relational table?
Anonymous Quiz
6%
Speed up joins only
83%
Uniquely identify each row
2%
Store the largest value
9%
Enforce a specific data type
Topic: Python
🔍 Quick look before the question:
🔍 Quick look before the question:
def outer():
x = 10
def inner():
nonlocal x
x += 5
return x
return inner
f = outer()
print(f())
print(f())
What does this print, in order?
Anonymous Quiz
28%
15 then 15
44%
15 then 20
6%
10 then 10
22%
This raises a SyntaxError because nonlocal can't modify enclosing scope
What does the 'volatile' keyword guarantee for a Java field?
Anonymous Quiz
8%
It makes the field immutable
15%
It guarantees atomic compound operations like count++
62%
It ensures reads and writes to the field are visible across threads, preventing stale caching
15%
It prevents the field from being garbage collected