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The correct answer is C: JdbcTemplate with Spring. JdbcTemplate in Spring Framework automatically manages JDBC resources and is the recommended approach in modern applications.

In Java, which of the following is true about abstract classes?

The correct answer is A: An abstract class can have no abstract methods. An abstract class can have zero or more abstract methods. It can also have concrete methods, constructors, and instance variables.

Which of the following best describes the purpose of the Runnable interface in Java?

The correct answer is B: It provides a way to define code that can be executed by a thread. The Runnable interface contains a single run() method that defines the code to be executed when a thread runs. It's preferred over extending Thread class.

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The correct answer is B: Returns false. next() returns false when the cursor is positioned beyond the last row, indicating no more rows available.

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Java Programming
Lambda Expressions

Java OOP, collections, multithreading

17 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 17

Topics in Java Programming

All Basics & Syntax 100 OOP in Java 100 Collections Framework 100 Multithreading 100 Exception Handling 100 I/O Streams 100 JDBC 100 Generics 100 Lambda Expressions 100 Spring Framework Basics 58

Q.1 Hard Lambda Expressions

What is the return type of a lambda expression used with IntStream.range(1, 5).map(x -> x * 2)?

A void

B int

C IntStream

D Function

Correct Answer: C. IntStream

EXPLANATION

map() is an intermediate operation that returns an IntStream. The lambda expression (x -> x * 2) transforms each int, but map() itself returns IntStream, not the transformed value type.

Test

Q.2 Hard Lambda Expressions

Which of the following best demonstrates the use of Optional with lambda expressions for safe null handling?

A Optional.of(value).map(x -> x.toUpperCase()).orElse("default")

B if (value != null) { value.toUpperCase(); }

C try { value.toUpperCase(); } catch (NullPointerException e) { }

D value != null ? value.toUpperCase() : "default"

Correct Answer: A. Optional.of(value).map(x -> x.toUpperCase()).orElse("default")

EXPLANATION

Optional with map() using a lambda expression is the functional programming approach. It's safe, readable, and chains operations effectively. Options B, C, and D are imperative approaches.

Test

Q.3 Hard Lambda Expressions

In the context of exception handling with lambda expressions, what happens if a lambda body throws a checked exception?

A The lambda expression automatically wraps it in RuntimeException

B It causes a compilation error unless the functional interface declares the exception

C It's always caught and ignored

D The functional interface must declare throws clause

Correct Answer: B. It causes a compilation error unless the functional interface declares the exception

EXPLANATION

If a lambda body throws a checked exception, it must be declared in the functional interface's method signature. Otherwise, compilation will fail.

Test

Q.4 Hard Lambda Expressions

What is the difference between a lambda expression and an anonymous inner class in Java?

A Lambda expressions are only for functional interfaces, while anonymous classes can implement any interface

B Lambda expressions are cleaner and more concise for functional interfaces

C Lambda expressions create new scope, while anonymous classes don't

D Both A and B

Correct Answer: D. Both A and B

EXPLANATION

Lambda expressions can only be used with functional interfaces (single abstract method), whereas anonymous classes can implement any interface. Lambda expressions are also more concise.

Test

Q.5 Hard Lambda Expressions

Consider a scenario where you need to sort a list of strings by length. Which lambda expression is most appropriate for Comparator?

A (s1, s2) -> s1.compareTo(s2)

B (s1, s2) -> Integer.compare(s1.length(), s2.length())

C (s1, s2) -> s1.length() - s2.length()

D Both B and C

Correct Answer: D. Both B and C

EXPLANATION

Both expressions correctly sort by length. Option B uses Integer.compare (safer for int overflow), while Option C uses direct subtraction. Both work correctly here.

Test

Q.6 Hard Lambda Expressions

What is the correct way to chain lambda expressions using Function interface?
Function f1 = x -> x * 2;
Function f2 = x -> x + 5;
How to apply f1 first, then f2?

A f1.andThen(f2).apply(3)

B f1.compose(f2).apply(3)

C f2.apply(f1.apply(3))

D A and C

Correct Answer: D. A and C

EXPLANATION

Both andThen and explicit composition order result in applying f1 first (3*2=6, then 6+5=11), equivalent to option C.

Test

Q.7 Hard Lambda Expressions

Consider: Stream.of(1, 2, 3).map(x -> { System.out.println(x); return x * 2; }).collect(Collectors.toList()); What will print?

A 1 2 3

B 2 4 6

C Nothing until the collect operation completes

D 1 2 3 2 4 6

Correct Answer: A. 1 2 3

EXPLANATION

map() is an intermediate operation. The println executes because collect() is a terminal operation that triggers evaluation. It prints 1, 2, 3 (the original values).

Test

Q.8 Hard Lambda Expressions

Consider: Function curried = a -> b -> a + b; What is this pattern called?

A Higher-order function with currying

B Nested lambda expression

C Function composition

D Stream reduction

Correct Answer: A. Higher-order function with currying

EXPLANATION

This is a curried function - a higher-order function that takes one argument and returns another function taking the next argument. It transforms multi-argument functions into sequences of single-argument functions.

Test

Q.9 Hard Lambda Expressions

What is the time complexity of reducing a stream with a stateful lambda operation?

A O(n) for sequential, O(log n) for parallel

B O(n) for both sequential and parallel streams

C O(1) regardless of stream size

D Depends on the operation and stream characteristics

Correct Answer: D. Depends on the operation and stream characteristics

EXPLANATION

Time complexity depends on the specific reduction operation, whether the lambda is stateless, and stream characteristics. Generally O(n), but parallelization overhead affects actual performance.

Test

Q.10 Hard Lambda Expressions

Consider: Function curry = x -> y -> x + y; What does curry.apply(5).apply(3) return?

A 8

B 15

C 5

D 3

Correct Answer: A. 8

EXPLANATION

This is a curried function. curry.apply(5) returns a function that adds 5. Applying that with 3 gives 5 + 3 = 8.

Test

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Lambda Expressions