Which statement correctly implements a generic factory method?

The correct answer is B: public static T create(Class clazz) throws Exception { return clazz.newInstance(); }. Cannot instantiate generic type T directly. Using Class.newInstance() is a valid pattern (though deprecated in newer Java versions in favor of getConstructor()). Option A is invalid.

What will be the output of: IntStream.range(1, 4).map(x -> x * 2).sum();

The correct answer is A: 12. range(1, 4) generates [1, 2, 3]. After map(x -> x * 2): [2, 4, 6]. Sum = 2 + 4 + 6 = 12.

Which collection class is synchronized by default?

The correct answer is C: Hashtable. Hashtable is a legacy synchronized collection class. HashMap, ArrayList, and TreeSet are not synchronized by default.

What will be the output? class Test { public static void main(String[] args) { int x = 10; { int x = 20; System.out.println(x); } System.out.println(x); } }

The correct answer is B: 20 10. A block scope creates a new variable x = 20 which shadows the outer x. First print outputs 20, then the block ends, outer x (10) is printed.

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Java Programming
Basics & Syntax

Java OOP, collections, multithreading

34 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–30 of 34

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.21 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.22 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.23 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.24 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

Q.25 Easy Basics & Syntax

What will be the output: String s = "Hello"; System.out.println(s.charAt(1));

A H

B e

C l

D o

Correct Answer: B. e

EXPLANATION

charAt() uses 0-based indexing. Index 1 refers to the second character, which is 'e' in "Hello".

Test

Q.26 Easy Basics & Syntax

Which of the following is the correct syntax for a multi-line comment in Java?

A // This is a comment

B /* This is a comment */

D # This is a comment

Correct Answer: B. /* This is a comment */

EXPLANATION

Multi-line comments in Java use /* */ syntax. Single-line comments use //. Other syntaxes are for different languages.

Test

Q.27 Easy Basics & Syntax

What will be printed? float f = 5.5f; System.out.println(f);

A 5.5

B 5.50

C Error

D 5

Correct Answer: A. 5.5

EXPLANATION

The 'f' suffix indicates a float literal. The output will be 5.5 (trailing zeros are not shown in standard printing).

Test

Q.28 Easy Basics & Syntax

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

A 123abc

B _myVar

C my-Var

D class

Correct Answer: B. _myVar

EXPLANATION

Variable names must start with a letter, underscore (_), or dollar sign ($). They cannot start with digits, contain hyphens, or be reserved keywords.

Test

Q.29 Easy Basics & Syntax

Which keyword is used to prevent a class from being inherited?

A static

B abstract

C final

D private

Correct Answer: C. final

EXPLANATION

The 'final' keyword prevents a class from being extended/inherited. A final class cannot have subclasses.

Test

Q.30 Easy Basics & Syntax

What will be the output of: System.out.println(5 / 2);

A 2.5

B 2

C 2.0

D Error

Correct Answer: B. 2

EXPLANATION

Integer division in Java results in an integer. 5/2 = 2 (remainder is discarded). To get 2.5, at least one operand must be float/double.

Test

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