Which of the following is thread-safe?

The correct answer is C: ConcurrentHashMap. ConcurrentHashMap is thread-safe and uses bucket-level locking. HashMap, TreeMap, and LinkedHashMap are not thread-safe.

Identify the output: System.out.println("Java".length());

The correct answer is A: 4. The length() method returns the number of characters in the string "Java", which is 4 characters.

Consider code: String query = "SELECT * FROM users WHERE id=" + userId; stmt.executeQuery(query); What security issue exists?

The correct answer is B: SQL Injection vulnerability. This is vulnerable to SQL injection as user input is directly concatenated. Using PreparedStatement with parameters prevents this: "SELECT * FROM users WHERE id=?"

When a static method is called on an instance of a class, what happens?

The correct answer is B: The method is called on the class, not the instance (though syntactically allowed). Static methods belong to the class, not instances. When called on an instance, Java internally calls the method on the class. Static methods cannot access instance variables or use 'this' keyword.

You need to read a file line by line efficiently. Which approach is best?

The correct answer is B: BufferedReader with readLine(). BufferedReader with readLine() is the most efficient and convenient way to read files line by line. It provides buffering and a dedicated method for reading lines.

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Java Programming
Spring Framework Basics

Java OOP, collections, multithreading

15 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–15 of 15

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.11 Easy Spring Framework Basics

Which XML element is used to define a bean in Spring XML configuration?

Correct Answer: B.

EXPLANATION

The <bean> element is the standard XML element used in applicationContext.xml to define Spring beans.

Test

Q.12 Easy Spring Framework Basics

What does @Autowired annotation do in Spring?

A Automatically injects dependencies by type

B Creates a new bean instance

C Marks a class as deprecated

D Enables auto-scanning of packages

Correct Answer: A. Automatically injects dependencies by type

EXPLANATION

@Autowired performs type-based dependency injection. Spring looks for a bean of the required type and injects it automatically.

Test

Q.13 Easy Spring Framework Basics

Which of the following is NOT a valid Spring bean scope in Spring 5.x+?

A singleton

B prototype

C request

D eternal

Correct Answer: D. eternal

EXPLANATION

Valid scopes are singleton, prototype, request, session, application, and websocket. 'eternal' is not a valid scope.

Test

Q.14 Easy Spring Framework Basics

What is the primary purpose of Dependency Injection (DI) in Spring Framework?

A To increase code complexity

B To reduce coupling between classes and improve testability

C To replace all design patterns

D To automatically generate SQL queries

Correct Answer: B. To reduce coupling between classes and improve testability

EXPLANATION

DI reduces coupling by injecting dependencies rather than creating them internally, making code more testable and maintainable.

Test

Q.15 Easy Spring Framework Basics

Which annotation is used to mark a class as a Spring Bean in the latest Spring Framework?

A @Bean

B @Component

C @Service

D @Controller

Correct Answer: B. @Component

EXPLANATION

@Component is a generic stereotype annotation for any Spring-managed component. @Bean is used on methods, while @Service and @Controller are specialized versions of @Component.

Test

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