Consider the declaration: List

The correct answer is B: List of Integer and its superclasses. '? super Integer' is a lower bounded wildcard that accepts Integer and all its superclasses like Number, Object. This allows write operations with Integer values.

Which of the following will compile successfully?

The correct answer is B: List list = new ArrayList();. Generics only work with reference types. 'int' is a primitive type, so 'Integer' wrapper class must be used instead.

Which of the following is a valid method name in Java?

The correct answer is B: _myMethod(). Method names must start with a letter, underscore, or dollar sign. '_myMethod()' is valid. Names cannot start with digits, contain hyphens, or spaces.

In Java exception handling, what is the order of execution in try-finally-catch block?

The correct answer is A: try → catch → finally. The correct order is try block executes first, then catch block (if exception occurs), and finally block always executes at the end.

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

The correct answer is D: Both A and C. Lambdas provide concise syntax, are compiled directly without separate class files, and work only with functional interfaces (single abstract method).

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Java Programming

Java OOP, collections, multithreading

476 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 51–60 of 476

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.51 Medium Lambda Expressions

What is the difference between Consumer and Function functional interfaces?

A Consumer returns a value, Function doesn't

B Function returns a value, Consumer doesn't

C Both are identical

D Consumer can have multiple parameters, Function cannot

Correct Answer: B. Function returns a value, Consumer doesn't

EXPLANATION

Function<T, R> takes parameter T and returns R. Consumer<T> takes parameter T and returns void.

Test

Q.52 Medium Lambda Expressions

Which functional interface should be used for a lambda with no parameters and no return value?

A Supplier

B Consumer

C Runnable

D Function

Correct Answer: C. Runnable

EXPLANATION

Runnable is the functional interface for operations with no parameters and no return value (void).

Test

Q.53 Medium Lambda Expressions

What will be the type of the lambda expression (x) -> x.toString()?

A Function

B Function

C Cannot be determined without context

D Consumer

Correct Answer: C. Cannot be determined without context

EXPLANATION

Without context, the parameter type cannot be inferred. The functional interface type determines the parameter type.

Test

Q.54 Medium Lambda Expressions

Which of the following lambda expressions has incorrect syntax?

A (int x) -> x * 2

B x -> x * 2

C (x, y) -> { return x + y; }

D (int x, int y) -> x > y ? x : y

Correct Answer: D. (int x, int y) -> x > y ? x : y

EXPLANATION

Ternary operator inside lambda requires braces and explicit return statement for type inference.

Test

Q.55 Medium Lambda Expressions

What will be the output of: List list = Arrays.asList(1, 2, 3); list.replaceAll(x -> x * 2); System.out.println(list);

A [1, 2, 3]

B [2, 4, 6]

C [] (empty list)

D [2, 2, 2]

Correct Answer: B. [2, 4, 6]

EXPLANATION

replaceAll() with a lambda expression modifies the list in-place, multiplying each element by 2. Result is [2, 4, 6].

Test

Q.56 Medium Lambda Expressions

What happens when a lambda expression references a local variable from its enclosing scope?

A The variable must be explicitly final or effectively final

B The variable is automatically copied into the lambda's scope

C Any variable can be accessed without restrictions

D The variable must be static

Correct Answer: A. The variable must be explicitly final or effectively final

EXPLANATION

Lambda expressions can only access local variables that are final or effectively final (not reassigned). This ensures thread-safety and consistency.

Test

Q.57 Medium Lambda Expressions

Which of the following correctly uses method reference with constructor?

A String::new

B new String::

C String->new

D new::String

Correct Answer: A. String::new

EXPLANATION

Constructor method references use ClassName::new syntax. String::new refers to the String constructor and can be used wherever a Supplier<String> is expected.

Test

Q.58 Medium Lambda Expressions

In the lambda expression (a, b) -> a.compareTo(b), what can we infer about the parameters?

A Both a and b are integers

B Both a and b are Comparable objects

C a is a String and b is a number

D Types cannot be determined without context

Correct Answer: D. Types cannot be determined without context

EXPLANATION

Without explicit type declarations or context, the compiler must infer types from usage. We can only determine they have a compareTo() method, likely Comparable types.

Test

Q.59 Medium Lambda Expressions

What will be the output of: IntStream.range(1, 4).map(x -> x * x).forEach(System.out::print);

A 149

B 123

C 111

D 000

Correct Answer: A. 149

EXPLANATION

range(1, 4) generates 1, 2, 3. map(x -> x * x) produces 1, 4, 9. Printed without spaces gives '149'.

Test

Q.60 Medium Lambda Expressions

What issue can arise when using lambda expressions with checked exceptions?

A Checked exceptions cannot be thrown directly in lambda expressions

B They must be wrapped in try-catch or a custom functional interface must be created

C Checked exceptions automatically become unchecked in lambdas

D Lambda expressions cannot handle any exceptions

Correct Answer: B. They must be wrapped in try-catch or a custom functional interface must be created

EXPLANATION

Since standard functional interfaces don't declare checked exceptions, you must either wrap in try-catch or create a custom functional interface that throws the checked exception.

Test

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