What is the PECS principle in generics?

The correct answer is A: Producer Extends, Consumer Super. PECS (Producer Extends, Consumer Super) is a mnemonic for wildcard bounds: use '? extends' when reading (producing), use '? super' when writing (consuming).

What is the output? public class Test { public static void main(String[] args) { int x = 0; try { x = 5; System.out.println(x / 0); x = 10; } catch (ArithmeticException e) { x = 15; } finally { System.out.println(x); } } }

The correct answer is C: 15. x becomes 5, then ArithmeticException occurs. x becomes 15 in catch block. Finally block prints 15.

What is the output of: System.out.println(10 * 2 / 5 * 2);

The correct answer is A: 8. Operators *, / have same precedence and are evaluated left to right: ((10 * 2) / 5) * 2 = (20 / 5) * 2 = 4 * 2 = 8.

What will be the output of: Supplier greeting = () -> "Hello"; System.out.println(greeting.get());

The correct answer is A: Hello. Supplier.get() returns the value produced by the lambda expression, which is "Hello".

In Java, what is the relationship between an interface and a class in terms of implementation?

The correct answer is A: A class can implement multiple interfaces but can extend only one class. Java supports multiple interface implementation but single class inheritance. A class uses 'implements' keyword for interfaces and 'extends' for classes. This is a fundamental OOP concept.

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Java OOP, collections, multithreading

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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.1 Medium Spring Framework Basics

What is the purpose of using @Bean method parameters in Spring @Configuration classes?

A To inject dependencies into the bean being created

B To pass configuration values from properties files

C To define bean relationships through method parameters

D Both A and C are correct

Correct Answer: D. Both A and C are correct

EXPLANATION

Method parameters in @Bean methods allow Spring to inject dependent beans and establish bean relationships, enabling dependency injection at bean creation time.

Test

Q.2 Medium Spring Framework Basics

In Spring Framework 6.0, what is the role of the @EnableAutoConfiguration annotation in Spring Boot?

A It enables automatic bean registration based on classpath contents

B It disables all manual bean configuration

C It is replaced by @SpringBootApplication in modern versions

D Both A and C are correct

Correct Answer: D. Both A and C are correct

EXPLANATION

@EnableAutoConfiguration (or @SpringBootApplication which includes it) auto-configures Spring beans based on jar dependencies on the classpath.

Test

Q.3 Medium Spring Framework Basics

What is the significance of the @Qualifier annotation when used alongside @Autowired in Spring?

A It improves performance of bean injection

B It specifies which bean to inject when multiple candidates exist

C It marks a bean as high quality

D It reduces memory consumption

Correct Answer: B. It specifies which bean to inject when multiple candidates exist

EXPLANATION

@Qualifier resolves ambiguity in autowiring by specifying the exact bean name or custom qualifier to inject when multiple beans of the same type exist.

Test

Q.4 Medium Spring Framework Basics

Which annotation is used to provide external configuration properties to Spring beans in the 2024 Spring Boot version?

A @PropertySource

B @ConfigurationProperties

C @Value

D All of the above

Correct Answer: D. All of the above

EXPLANATION

@PropertySource loads properties from files, @ConfigurationProperties binds properties to bean properties, and @Value injects individual values. All are used for configuration.

Test

Q.5 Medium Spring Framework Basics

What happens when @Lazy annotation is applied to a singleton bean in Spring?

A The bean is created only when first accessed

B The bean is created at application startup

C The bean is never created

D The bean is created in a separate thread

Correct Answer: A. The bean is created only when first accessed

EXPLANATION

@Lazy defers bean instantiation until it's first requested, overriding the default eager initialization behavior of singleton beans.

Test

Q.6 Medium Spring Framework Basics

In Spring Framework, which interface represents a factory pattern implementation for creating objects?

A ObjectFactory

B FactoryBean

C BeanFactory

D All of the above

Correct Answer: D. All of the above

EXPLANATION

BeanFactory is the basic container, ObjectFactory is for lazy bean retrieval, and FactoryBean allows custom bean creation logic. All represent factory patterns in Spring.

Test

Q.7 Medium Spring Framework Basics

What is the role of Spring's PropertyPlaceholderConfigurer in application configuration?

A It encrypts sensitive properties

B It replaces ${} placeholders with values from properties files

C It validates XML configuration files

D It manages database transactions

Correct Answer: B. It replaces ${} placeholders with values from properties files

EXPLANATION

PropertyPlaceholderConfigurer (or @PropertySource in modern Spring) enables externalization of configuration by replacing ${property.name} placeholders with actual values from properties files.

Test

Q.8 Medium Spring Framework Basics

Consider a scenario where a Spring application needs to initialize a database connection pool at startup. Which method should be used?

A Use @PostConstruct annotation on a method

B Use InitializingBean interface

C Use initMethod parameter in @Bean

D All of the above are valid approaches

Correct Answer: D. All of the above are valid approaches

EXPLANATION

Spring provides multiple mechanisms for initialization: @PostConstruct, InitializingBean interface, and initMethod in @Bean definition. All are equally valid.

Test

Q.9 Medium Spring Framework Basics

What is the difference between @Bean and @Component annotations in Spring?

A @Bean is class-level while @Component is method-level

B @Bean is method-level while @Component is class-level

C They are functionally identical with no difference

D @Bean cannot be used in @Configuration classes

Correct Answer: B. @Bean is method-level while @Component is class-level

EXPLANATION

@Component is applied to classes making them beans automatically. @Bean is applied to methods in @Configuration classes, giving explicit control over bean creation.

Test

Q.10 Medium Spring Framework Basics

In Spring Framework, what does the @Autowired annotation do when autowiring candidates are ambiguous?

A It automatically selects the first bean found

B It throws NoUniqueBeanDefinitionException

C It uses the @Primary annotation to resolve conflicts

D Both B and C are correct

Correct Answer: D. Both B and C are correct

EXPLANATION

When multiple beans match the injection point, Spring throws an exception unless @Primary is used to indicate the preferred bean or @Qualifier specifies which bean to inject.

Test

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