Top 10 Java8 Interview Question and Answers

 

Q.1: What are the major new features in Java 8? 

Ans: Java 8 introduced several new features, including lambdas, functional interfaces, the Stream API, default methods in interfaces, and the Date and Time API.

 

Q.2: What is a lambda expression in Java 8?

Ans: A lambda expression is a lightweight syntax for creating anonymous functions in Java. It can be used to pass behavior as an argument to a method, or to define a method that can be passed as an argument to another method.

 

Q.3: What is a functional interface in Java 8?

Ans: A functional interface is an interface that has exactly one abstract method. It is used to define a contract for a lambda expression or method reference. The @FunctionalInterface annotation can be used to enforce the single abstract method constraint.

 

Q.4: What is the Stream API in Java 8?

Ans: The Stream API is a new API in Java 8 that allows for functional-style processing of collections. It provides a declarative way to perform operations like filtering, mapping, and reducing on a collection.

 

Q.5: What are default methods in interfaces in Java 8?

Ans: Default methods in interfaces are methods that have an implementation, but can be overridden by implementing classes. They were added to interfaces in Java 8 to allow for evolution of interfaces without breaking existing code.

 

Q.6: What is the Date and Time API in Java 8?

Ans: The Date and Time API is a new API in Java 8 for working with dates, times, and time zones. It provides a more comprehensive and flexible way to work with dates and times than the previous Date and Calendar APIs.

 

Q.7: What is the difference between the java.util.Date and java.time.LocalDate classes?

Ans: The java.util.Date class represents a point in time, while the java.time.LocalDate class represents a date without a time. The LocalDate class is also immutable and thread-safe, while the Date class is mutable and not thread-safe.

 

Q.8: How do you create a stream in Java 8?

Ans: You can create a stream in Java 8 by calling the stream() method on a collection, or by using the of() or generate() methods of the Stream class. You can also create a stream from an array using the Arrays.stream() method.

 

Q.9: What is method reference in Java 8?

Ans: A method reference is a shorthand syntax for creating a lambda expression that calls a method. It can be used to pass a method as an argument to another method, or to define a lambda expression that calls a method.

 

Q.10: What is the difference between a Consumer and a Supplier in Java 8?

Ans: A Consumer is a functional interface that takes a single argument and returns no result, while a Supplier is a functional interface that takes no arguments and returns a result. They are both used in the Stream API for processing elements of a stream.