Java 8 Features Interview Questions

  1. What are the main features of Java 8?
    • Lambda expressions
    • Stream API
    • Default methods in interfaces
      Functional interfaces
    • Date and Time API (JSR 310)
  2. What are Lambda expressions in Java 8?
    • Lambda expressions are a way to define anonymous methods that can be used as function arguments. They allow for concise code and can be used to pass behavior as a method argument.
  3. What is the Stream API in Java 8?
    • The Stream API is a new feature in Java 8 that allows for processing of collections of data in a declarative and functional way. Streams allow for more concise and readable code, as well as improved performance in certain cases.
  4. What are default methods in interfaces?
    • Default methods are methods that have a default implementation in an interface. They allow for backwards compatibility in existing interfaces while still allowing new functionality to be added.
  5. What is a functional interface in Java 8?
    • A functional interface is an interface that has only one abstract method. Functional interfaces are used in conjunction with lambda expressions to provide a concise way of defining behavior.
  6. What is the Date and Time API in Java 8?
    • The Date and Time API (JSR 310) is a new API in Java 8 that provides a more comprehensive and flexible way of handling dates and times in Java. It includes classes for dates, times, durations, and intervals, as well as support for time zones and calendars.
  7. What is the syntax for using Lambda expressions in Java 8?
    • The syntax for Lambda expressions is as follows:
    • (parameter1, parameter2, …) -> { // code to be executed }
    • Where the parameters are defined in the parentheses, followed by the arrow (->) and the code to be executed in curly braces ({ }).
  8. What are some benefits of using the Stream API in Java 8?
    • The Stream API can provide several benefits, such as:
    • More concise and readable code
    • Improved performance in certain cases, especially when working with large data sets
    • Automatic parallelization of operations on the data, if applicable
    • Support for lazy evaluation, which can improve performance by avoiding unnecessary computations
  9. How can default methods in interfaces be used for backwards compatibility?
    • Default methods provide a default implementation for an interface method, allowing existing code that implements the interface to continue working without needing to implement the new method. This provides backwards compatibility while still allowing new functionality to be added to the interface.
  10. How can the Date and Time API in Java 8 be used to handle time zones?
    • The Date and Time API provides a ZoneId class that can be used to represent a time zone. This class can be used to convert between time zones, as well as to perform calculations based on different time zones. The API also provides classes for representing date and time values in different time zones, such as ZonedDateTime.

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