What is the difference between and ?

The correct answer is B: First ensures T is comparable with itself; second is a raw type. is a recursive bound ensuring T implements Comparable of its own type. uses raw type, losing type information.

Which keyword is used to prevent method overriding in Java?

The correct answer is B: final. The 'final' keyword prevents a method from being overridden by subclasses.

Which of the following lambda expressions has incorrect syntax?

The correct answer is D: (int x, int y) -> x > y ? x : y. Ternary operator inside lambda requires braces and explicit return statement for type inference.

Which of the following is the correct way to close JDBC resources to prevent resource leaks?

The correct answer is D: Both A and C are correct. Resources should be closed in reverse order of creation (ResultSet → Statement → Connection), or preferably using try-with-resources which auto-closes resources.

What does the following generic method signature indicate? public static T findMax(T[] array)

The correct answer is A: T must implement Comparable interface parameterized with itself. The bounded type parameter 'T extends Comparable' enforces that T must implement Comparable and be comparable with its own type. This is the F-bounded polymorphism pattern.

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Java OOP, collections, multithreading

270 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–50 of 270

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.41 Easy Lambda Expressions

In Java 8, a lambda expression can access local variables from its enclosing scope. What is the constraint on these variables?

A They must be declared as final or effectively final

B They must be static variables

C They must be instance variables of the class

D They can be modified freely within the lambda

Correct Answer: A. They must be declared as final or effectively final

EXPLANATION

Lambda expressions can only access local variables that are final or effectively final to ensure thread safety and immutability.

Test

Q.42 Easy Lambda Expressions

What is the output of this code?
Consumer print = s -> System.out.println(s.toUpperCase());
print.accept("java");

A java

B JAVA

C Compilation error

D java JAVA

Correct Answer: B. JAVA

EXPLANATION

Consumer accepts one argument and returns nothing. print.accept("java") calls lambda which prints s.toUpperCase() = "JAVA".

Test

Q.43 Easy Lambda Expressions

What will be the output of the following code?
UnaryOperator square = x -> x * x;
System.out.println(square.apply(5));

A 25

B 5

C Compilation error

D Runtime error

Correct Answer: A. 25

EXPLANATION

UnaryOperator applies a function on its argument and returns result of same type. square.apply(5) returns 5*5 = 25.

Test

Q.44 Easy Lambda Expressions

Which package contains the built-in functional interfaces in Java?

A java.util.function

B java.lang.function

C java.io.function

D java.util.interface

Correct Answer: A. java.util.function

EXPLANATION

The java.util.function package contains functional interfaces like Predicate, Consumer, Function, Supplier, and BiFunction introduced in Java 8.

Test

Q.45 Easy Lambda Expressions

What is a functional interface in Java?

A An interface with exactly one abstract method

B An interface that extends multiple interfaces

C An interface with default methods only

D An interface with no methods

Correct Answer: A. An interface with exactly one abstract method

EXPLANATION

A functional interface has exactly one abstract method. It can have multiple default methods. The @FunctionalInterface annotation can be used to mark it.

Test

Q.46 Easy Lambda Expressions

Which of the following is a valid lambda expression syntax in Java?

A (int x, int y) -> x + y

B (x, y) => x + y

C [x, y] -> x + y

D (x, y) : x + y

Correct Answer: A. (int x, int y) -> x + y

EXPLANATION

Valid Java lambda syntax uses arrow operator (->). Parameters can be typed or untyped, and the expression or block follows the arrow.

Test

Q.47 Easy Lambda Expressions

What is the primary purpose of lambda expressions introduced in Java 8?

A To provide a concise syntax for implementing functional interfaces

B To replace all anonymous inner classes

C To improve memory management

D To simplify exception handling

Correct Answer: A. To provide a concise syntax for implementing functional interfaces

EXPLANATION

Lambda expressions provide a concise way to implement single abstract method (functional interfaces) without verbose anonymous class syntax.

Test

Q.48 Easy Generics

When using bounded type parameters with multiple interfaces, what is the correct syntax in Java?

Correct Answer: A.

EXPLANATION

Java uses ampersand (&) to combine multiple bounds. The class must appear first, followed by interfaces. Commas, pipes, and 'implements' keyword are not valid syntax for type parameter bounds.

Test

Q.49 Easy Generics

In a Spring Boot application, you need to create a generic repository interface that works with any entity type. Which declaration correctly implements this pattern?

A public interface GenericRepository { T findById(Long id); void save(T entity); }

B public interface GenericRepository { Object findById(Long id); void save(Object entity); }

C public interface GenericRepository { T findById(Long id); void save(T entity); }

D public interface GenericRepository { T findById(K id); void save(T entity); }

Correct Answer: A. public interface GenericRepository { T findById(Long id); void save(T entity); }

EXPLANATION

Option A uses single type parameter T for entity type, which is the standard pattern for generic repositories. Option C is redundant (all classes extend Object), and Option D adds unnecessary complexity.

Test

Q.50 Easy Generics

Which declaration is valid in Java Generics?

A List list = new ArrayList();

B List list = new ArrayList();

C List list = new ArrayList();

D List

Correct Answer: B. List list = new ArrayList();

EXPLANATION

Generics only work with reference types, not primitive types. Integer is the wrapper class for int, making option B valid.

Test

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