Top 250 Java Interview Questions and Answers

No, the 'this' keyword cannot be equal to null.

• The 'this' keyword refers to the current instance of a class.

• It is used to access the members of the current object.

• Since 'this' refers to an object, it cannot be null.

Spring bean scope defines the lifecycle and visibility of a bean in the Spring container.

• Singleton scope: Only one instance of the bean is created and shared across the application.

• Prototype scope: A new instance of the bean is created every time it ...read more

C code in Java refers to the use of the Java Native Interface (JNI) to incorporate C code into Java programs.

• C code in Java is typically used when performance optimization or low-level system access is required.

• JNI allows Java programs to call C func...read more

Spring IOC is a container that manages the lifecycle of Java objects. Dependency Injection is a design pattern that allows objects to be loosely coupled.

• Spring IOC is a container that manages the creation and destruction of objects

• Dependency Injectio...read more

Runnable interface is used for running a task, while Callable interface is used for returning a result after running a task.

• Runnable interface has a run() method that does not return any value.

• Callable interface has a call() method that returns a val...read more

Calculate the day of the week for September 14, given January 1 is a Monday.

• January 1 is a Monday.

• Count the total days from January 1 to September 14.

• Days in each month: Jan(31), Feb(28), Mar(31), Apr(30), May(31), Jun(30), Jul(31), Aug(31), Sep(14)....read more

@SpringBootApplication is a Spring Boot annotation that enables auto-configuration and component scanning.

• Enables auto-configuration of the Spring application context

• Enables component scanning for beans

• Provides a convenient shortcut for @Configuratio...read more

This Java program counts the occurrences of the letter 'E' in the string 'SELENIUM'.

• Use a loop to iterate through each character of the string.

• Check if the character is 'E' (case-sensitive).

• Maintain a counter to keep track of the occurrences.

• Example:...read more

Use two threads to print even and odd numbers in increasing order.

• Create two threads, one for printing even numbers and one for printing odd numbers.

• Use a shared variable to keep track of the current number to be printed.

• Synchronize access to the sha...read more

Dependency Injection in Spring Boot is a design pattern that allows for better code management and testing by injecting dependencies.

• Promotes loose coupling between components.

• Facilitates easier unit testing by allowing mock dependencies.

• Implemented ...read more

Default methods in Java 8 allow interfaces to have method implementations, enhancing flexibility and backward compatibility.

• Enable adding new methods to interfaces without breaking existing implementations.

• Facilitate multiple inheritance of behavior ...read more

completableFuture is a class in Java that represents a future result of an asynchronous computation.

• It is used for asynchronous programming in Java.

• It can be used to chain multiple asynchronous operations.

• It supports callbacks and combinators.

• It can ...read more

Spring Sleuth is a distributed tracing solution for Spring applications, enabling monitoring and debugging of microservices.

• Integrates with Spring Cloud to provide tracing capabilities.

• Automatically adds trace and span IDs to logs for better correlat...read more

The @Controller annotation is used to create a controller class in Spring MVC, while @RestController is used to create RESTful web services.

• The @Controller annotation is used to create a controller class in Spring MVC, which is used to handle traditi...read more

Spring annotations are used to provide metadata to Spring framework classes and methods.

• Annotations like @Component, @Controller, @Service, and @Repository are used for component scanning and auto-wiring.

• @Autowired is used for dependency injection.

• @R...read more

Component Scan is a Spring framework feature that automatically detects and registers beans in the application context.

• It uses annotations like @Component, @Service, @Repository, and @Controller to identify beans.

• Configured via @ComponentScan annotat...read more

Java offers platform independence, strong community support, and robust security features, making it ideal for diverse applications.

• Platform Independence: Java's 'Write Once, Run Anywhere' capability allows applications to run on any device with a Ja...read more

Functional interfaces provide clarity and enforce single abstract method constraint.

• Functional interfaces provide clarity to developers by explicitly indicating that the interface is intended to be used as a functional interface.

• Using @FunctionalInte...read more

Monitoring Java applications with New Relic involves setting up agents and configuring alerts.

• Install New Relic Java agent in the application server

• Configure New Relic settings in the newrelic.yml file

• Set up custom dashboards and alerts in New Relic ...read more

Front Controller in Spring MVC is a design pattern that handles all requests and acts as a central point of control.

• Front Controller is a servlet in Spring MVC that receives all requests and then dispatches them to the appropriate handlers.

• It helps i...read more

Intermediate operations return a stream and do not produce a result, while terminal operations produce a result.

• Intermediate operations are lazy and do not execute until a terminal operation is called

• Examples of intermediate operations include filter...read more

Functional interfaces are interfaces with a single abstract method, enabling lambda expressions in Java.

• A functional interface can have multiple default or static methods.

• It is annotated with @FunctionalInterface for clarity.

• Example: Runnable (void r...read more

Spring actuators are devices that use the force generated by a spring to move or control a mechanism.

• Spring actuators convert the potential energy stored in a spring into mechanical motion.

• They are commonly used in various applications such as valves...read more

I am most familiar with the Spring framework, known for its comprehensive features for building Java applications.

• Dependency Injection: Spring's core feature that promotes loose coupling. Example: Using @Autowired to inject beans.

• Aspect-Oriented Prog...read more

Groups and View Groups are components of Android UI that help in organizing and displaying UI elements.

• View Groups are containers that hold other UI elements, such as LinearLayout, RelativeLayout, etc.

• Groups are a type of View Group that allow for th...read more

Lists allow duplicates and maintain order; sets are unique and unordered collections.

• List allows duplicate elements, e.g., List<String> list = Arrays.asList('A', 'B', 'A');

• Set does not allow duplicates, e.g., Set<String> set = new HashSet<>(Arrays.as...read more

Java elements in Selenium can be found using various methods like findElement, findElements, etc.

• Use findElement method to locate a single element in the DOM

• Use findElements method to locate multiple elements in the DOM

• Locate elements by ID, class na...read more