Java 8 Interview Questions For Experienced
Top 10 Java 8 Interview Questions for Experienced Professionals
Java 8 is the latest release of the popular programming language Java. As an experienced Java developer, you may be expected to have a strong understanding of the new features and changes introduced in Java 8. Some common interview questions that may be asked to assess your knowledge of Java 8 include questions about lambda expressions, functional interfaces, streams, default methods, and optional class. Additionally, you may be asked about the benefits and drawbacks of these new features, their impact on existing codes, and how to handle concurrency. You should also be familiar with the concept of parallel streams, default methods in interfaces, and the new date/time API. Being prepared to answer these questions will help you showcase your expertise in Java 8 and stand out in the interview process.
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1 - What are the new features introduced in Java 8?
Java 8 introduced several new features such as Lambda Expressions, Functional Interfaces, Default and Static Methods in Interfaces, Stream API, Date/Time API, and Optional class.
2) What is a Lambda Expression?
Lambda Expressions in Java 8 are anonymous functions that allow us to write more concise and readable code. They are useful for implementing functional interfaces as they provide a way to pass behavior as a method argument.
3) Can Lambda Expressions access local variables?
Yes, Lambda Expressions can access final or effectively final local variables. This is achieved through a process called “capturing.”
4) What is a Functional Interface?
A Functional Interface in Java 8 is an interface that contains only one abstract method. It can have any number of default and static methods but only one abstract method.
5) What is the purpose of Default and Static Methods in Interfaces?
Default methods in interfaces allow us to add new methods to existing interfaces without breaking the implementation of classes that implement them. Static methods, on the other hand, provide a way to implement utility methods that are commonly used by all classes that implement the interface.
6) What is the Stream API?
The Stream API in Java 8 provides a functional approach to processing collections of data. It allows us to perform filtering, mapping, and aggregating operations on collections using functional-style code.
7) How is the Date/Time API improved in Java 8?
Java 8 introduced a new Date/Time API that is more robust and developer-friendly. It provides classes such as LocalDate, LocalTime, and LocalDateTime for representing date and time without timezone information, and classes such as ZonedDateTime for representing date and time with timezone information.
8) What is Optional class?
The Optional class in Java 8 is a container object that may or may not contain a non-null value. It is primarily used to prevent NullPointerExceptions and to handle null values in a more elegant way.
9) How can we create an Optional object in Java 8?
We can create an Optional object by using the static method Optional.of() or Optional.ofNullable(). The former throws an exception if a null value is passed, while the latter creates an empty Optional object if a null value is passed.
10) What is a Method Reference?
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A Method Reference in Java 8 is a shorthand notation for writing Lambda Expressions that only call an existing method. It provides more readable and concise code by removing the verbose lambda expression syntax.
11) What is the difference between Iterable and Stream?
Both Iterable and Stream are used for processing collections of data, but they differ in their approach. Iterable is based on the Pull paradigm, meaning the elements are pulled one by one from the collection. On the other hand, Stream is based on the Push paradigm, meaning the elements are pushed and processed automatically.
12) Can we modify a Stream's source data?
No, Streams are immutable, and we cannot modify the source data. Instead, we need to use intermediate operations such as map or filter to create a new Stream with the desired modifications.
13) What is the purpose of the collect() method in Streams?
The collect() method is used to perform a mutable reduction operation on the elements of a Stream. It collects the elements into a data structure such as a List, Set, or Map.
14) How does the new Date/Time API handle timezones?
The new Date/Time API handles timezones by using the ZoneId class to represent a specific time zone. It also provides methods to convert between different timezones.
15) Can we use Java 8 features in older versions of Java?
No, Java 8 features are only available in Java 8 and above versions. They cannot be used in older versions of Java.
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