Java 8 Interview Questions | Some Frequently asked

Java 8 introduced several new features that revolutionized the way Java developers write code. Java 8 interview questions to focus on these new features, such as lambda expressions, streams, default methods in interfaces, the Optional class, and the Date and Time API. Interviewers may ask questions related to the purpose and usage of these features, as well as how they compare to older approaches. Additionally, questions may focus on functional programming concepts, such as functional interfaces and method references. It is important for Java developers to have a solid understanding of these features and concepts in order to succeed in Java 8 interviews.

Java 8 Interview Questions

1.What are the new features introduced in Java 8?

Java 8 introduced several new features including lambda expressions, streams, default methods in interfaces, the Optional class, the Date and Time API, and more.

2.What is a lambda expression in Java 8? How is it useful?

A lambda expression is an anonymous function that can be passed as an argument to a method or stored in a variable. It allows for more concise and expressive code, and can be used for functional programming.

3.What is the difference between a stream and a collection in Java 8?

A collection is a data structure that holds a collection of elements, while a stream is a sequence of elements that can be processed in parallel or in sequence. Streams provide a functional and concise way to process collections.

4.What are the default methods in Java 8 interfaces?

Default methods in interfaces provide a way to add new methods to an interface without breaking the existing implementations. They have a default implementation that can be overridden by the implementing classes.

5.How is the Optional class used in Java 8?

The Optional class is used to represent a value that may or may not be present. It is useful for handling null values and avoiding null pointer exceptions.

6.What is the new Date and Time API in Java 8? How is it better than the old Date and Calendar classes?

The new Date and Time API in Java 8 provides a more comprehensive and flexible way to handle dates and times. It is easier to use and less error-prone than the old Date and Calendar classes.

7.What is the purpose of the functional interface in Java 8?

The functional interface in Java 8 is an interface that has only one abstract method. It is used to enable functional programming in Java, and is the basis for lambda expressions and method references.

8.How is the parallel stream in Java 8 different from the sequential stream?

A parallel stream in Java 8 processes the elements of a stream in parallel, using multiple threads. This can be faster for large collections, but requires more overhead. A sequential stream processes the elements in a single thread.

9.What is the purpose of the @FunctionalInterface annotation in Java 8?

The @FunctionalInterface annotation is used to indicate that an interface is a functional interface, meaning it has only one abstract method. This annotation is optional, but can help prevent accidental additions of new abstract methods.

10.How can you use the method reference feature in Java 8?

The method reference feature in Java 8 allows you to refer to a method by its name without invoking it. It can be used in place of a lambda expression when the method being referenced matches the signature of the functional interface.

11.What is the difference between a predicate and a function in Java 8?

A predicate is a functional interface that takes a single argument and returns a boolean value, while a function takes one or more arguments and returns a value. Predicates are used to test a condition, while functions are used to transform data.

12.What is the difference between a supplier and a consumer in Java 8?

A supplier is a functional interface that takes no arguments and returns a value, while a consumer takes one argument and returns no value. Suppliers are used to generate values, while consumers are used to consume them.

13.What is the purpose of the peek method in a stream in Java 8?

The peek method in a stream in Java 8 allows you to perform a side-effect operation on each element of the stream, without changing the elements themselves. It is useful for debugging and logging.

Conclusion

Java 8 has introduced several new features that have fundamentally changed the way Java developers write code. To succeed in Java 8 interviews, it is essential for developers to have a solid understanding of these new features and concepts, such as lambda expressions, streams, default methods in interfaces, the Optional class, and the Date and Time API. Functional programming concepts, like functional interfaces and method references, are also critical to understand. Interviewers will often focus on these topics, so it is important for Java developers to prepare well and demonstrate their expertise in these areas. By mastering Java 8 features and concepts, Java developers can stand out in the job market and increase their chances of success in interviews.