Consider this generic interface: interface Comparable { int compareTo(T o); } Which class definition correctly implements this?

The correct answer is A: class MyClass implements Comparable { public int compareTo(MyClass o) { return 0; } }. Option A correctly implements the generic interface by specifying the concrete type parameter as MyClass in the implements clause.

What is Connection pooling in JDBC and why is it used?

The correct answer is B: Reusing database connections to improve performance and reduce overhead. Connection pooling maintains a pool of reusable connections, reducing the cost of creating new connections repeatedly.

What is the difference between throw and throws?

The correct answer is A: throw creates exception, throws declares it. 'throw' keyword actually throws an exception object. 'throws' keyword declares that a method throws a checked exception.

Which of the following is NOT a characteristic of Exception class in Java?

The correct answer is B: It is always checked exception. Exception class has both checked subclasses (like IOException) and unchecked subclasses (like RuntimeException). Not all exceptions extending Exception are checked.

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

The correct answer is D: Depends on the operation and stream characteristics. 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.

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Java Programming

Java OOP, collections, multithreading

270 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 251–260 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.251 Easy Basics & Syntax

Consider the code: int x = 5; x += 3; What is the value of x?

A 5

B 8

C 3

D 53

Correct Answer: B. 8

EXPLANATION

The compound assignment operator += means x = x + 3. So 5 + 3 = 8.

Test

Q.252 Easy Basics & Syntax

What will be the output of: System.out.println(10 / 3);

A 3.33

B 3

C 3.333333

D Compilation Error

Correct Answer: B. 3

EXPLANATION

Both operands are integers, so integer division is performed. Result is 3 (not 3.33). To get decimal, at least one operand must be float/double.

Test

Q.253 Easy Basics & Syntax

What is the purpose of the 'instanceof' operator?

A To create new instances

B To check if an object is an instance of a class

C To compare object values

D To delete object instances

Correct Answer: B. To check if an object is an instance of a class

EXPLANATION

The 'instanceof' operator is used to check if an object is an instance of a specific class or implements a specific interface.

Test

Q.254 Easy Basics & Syntax

What does the 'super' keyword do in Java?

A Refers to the current object

B Refers to the parent class

C Creates a new instance

D Marks a method as superior

Correct Answer: B. Refers to the parent class

EXPLANATION

The 'super' keyword is used to refer to parent class members and invoke parent class constructors.

Test

Q.255 Easy Basics & Syntax

Which of the following is a valid variable declaration?

A int 2num;

B int num-2;

C int num$2;

D int num.2;

Correct Answer: C. int num$2;

EXPLANATION

Variable names can contain letters, digits, underscores, and dollar signs, but cannot start with a digit or contain hyphens or dots.

Test

Q.256 Easy Basics & Syntax

What is the correct way to declare a constant in Java?

A const int MAX = 100;

B static int MAX = 100;

C public static final int MAX = 100;

D final static int MAX = 100;

Correct Answer: C. public static final int MAX = 100;

EXPLANATION

'const' is not a Java keyword. The correct convention for constants is public static final. Option D also works but C follows the standard convention.

Test

Q.257 Easy Basics & Syntax

Which of the following statements about Java packages is correct?

A Package names must be in uppercase

B Package names use dot notation for hierarchy

C A single Java file can belong to multiple packages

D Package statement must appear after import statements

Correct Answer: B. Package names use dot notation for hierarchy

EXPLANATION

Package names follow a hierarchical structure using dots (e.g., com.example.app). Package statement must be the first non-comment statement.

Test

Q.258 Easy Basics & Syntax

Which keyword is used to prevent method overriding in Java?

A abstract

B final

C static

D synchronized

Correct Answer: B. final

EXPLANATION

The 'final' keyword prevents a method from being overridden by subclasses.

Test

Q.259 Easy Basics & Syntax

Which of the following is NOT a valid Java identifier?

A _variable123

B $myVar

C 123variable

D my_Var$

Correct Answer: C. 123variable

EXPLANATION

Java identifiers cannot start with a digit. Valid identifiers must start with a letter, underscore, or dollar sign.

Test

Q.260 Easy Basics & Syntax

What will be the output of: System.out.println(Math.max(5, 10) - Math.min(3, 8));

A 2

B 5

C 7

D 15

Correct Answer: C. 7

EXPLANATION

Math.max(5, 10) = 10, Math.min(3, 8) = 3. So 10 - 3 = 7.

Test

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