Top 15 Java8 Interview questions for beginners

 

Q1. Explain the new features added in Java 8 

• Lambda Expressions - Used to define a function that can be referenced as an object.
• Functional Interface - Interfaces with just one abstract method.
• Method References - Allow us to use functions as parameters for invoking a method.
• Optional class - A wrapper class used to check Null values.
• Default Methods - Allows us to add implementation for methods inside an interface.
• Stream API - Special iterator class that allows pipeline processing of data.
• Date API - An improved API inspired by JodaTime.
• ForEach () method- to iterate the elements.
• Parallel Array Sorting- Array class which is used to sort array elements parallel.
• JDBC Enhancements- The JDBC-ODBC Bridge has been removed
• Base64 Encode Decode- class Base64 to deal with encryption.

Q2. What are the advantages of Java 8?

• Improved code readability and reusability.
• Small boilerplate code.
• Better stability
• Parallel execution of operations.
• compact code

Q3. What is a Lambda Expression?

Lambda expressions are a new and important feature of Java that was included in Java SE 8. It provides a clear and concise way to use expressions to represent method interfaces. Very useful in collection libraries. This is useful for iterating, filtering, and extracting data from the collection.

Q4. What is the use of Lambda Expression?

·         Provides an implementation of the functional interface.

·         Less coding.

Q5. What are Functional Interfaces?

An interface that has only one abstract method is called a functional interface. Java provides the @FunctionalInterface annotation used to declare an interface as a functional interface.

Q6. What does Method Reference mean in Java 8?

A method reference is a way to reference a method without calling it. The colon (: :) is used as the method reference. Method references are used to treat methods as lambda expressions.

Q7. What is Java 8 Streams?

A stream is like a set of objects retrieved from a source such as a collection. These are used to perform aggregated operations on data in a pipeline fashion. These are used to make the processing of data easier and easier. You can use Stream to filter, collect, print, convert one data structure to another, and more.

Q8. What do you mean by Default Methods?

Java provides the ability to create standard methods within an interface. Methods that are defined in the interface and marked as default are called default methods. These methods are non-abstract methods. Default keyword is used to create default methods.

Q9. Explain the forEach () method with the help of an example.

The forEach () method is part of the Stream API. It is used to iterate over each element of the stream to perform an action. Collection classes that extend the Iterable interface can iterate over elements using forEach loops.

import java.util.ArrayList;

public class ForEachExample {

public static void main (String [] args) {

List gamesList = new ArrayList ();

gamesList.add ("Soccer");

gamesList.add ("Cricket");

gamesList.add ("ches");

gamesList.add ("Hockey");

System.out.println ("------------ Iteration by passing a lambda expression --------------");

gamesList.forEach (games-> System.out.println (games));

}

}

 

Q10. What is Optional, and why is it used?

You can optionally have a container or wrapper class that can contain 0 or 1 values. This class contains methods to check if a value exists. This class is used as the return type for methods that may return null. This method should return an object, not a value. This helps avoid NullPointerException.Optional class provides methods which are used to check the presence of value for particular variable.

 

 

Q11. What is Java Base64 Encode and Decode, and why is it used?

Java provides Base64 classes for encryption. You can use the methods provided to encrypt and decrypt your data. To use the method, you need to import java.util.Base64 into your source file.

Q12. What is Stream Filter, and why is it used?

Java Stream provides a filter () method for filtering stream elements based on the specified predicate. If you want to get only the elements of the list, you can easily get them using the filter method.

Q13. What is String Joiner class used for?

Java has added a new final class, StringJoiner, to the java.util package. Used to create a sequence of characters separated by a delimiter. You can now create a string by passing a delimiter such as a comma (,) or dash (-). You can also pass a prefix and suffix to the string.

Q14. What is Java Nashron?

Nashron is a JavaScript engine. It is used to dynamically execute JavaScript code in the JVM (Java Virtual Machine). Java provides jjs, a command line tool used to execute JavaScript code.
You can use the jjs command line tool to execute JavaScript code and embed it in your Java source code.

Q15. What is Java Parallel Array Sorting?

Java provides a new additional function of the Array class used to sort array elements in parallel. The method is called parallelSort () and is overloaded for objects that are equivalent to all primitive data types.