Hi Readers, In this article we have compiled some important and frequently asked questions from Java 8. Java 8 interview questions and answers are available for beginners, those with 5 years of experience, those with 10 years of experience, and those with 12 years of experience.
Table of Contents
What are some of the new features in JAVA 8?
In Java 8, plenty of new features have been included. Here’s a list of key features:
- Functional Interface
- Default methods
- Lambda Expressions
- Method References
- Optional Class
- Date and Stream API
- Nashorn, JavaScript Engine
Java 8 belongs to which programming paradigm?
Java is an object-oriented programming language, therefore it’s only natural that Java 8 will be about object-oriented programming. Aside from object-oriented programming, Java 8 also belongs to functional, procedural, and logic programming language.
What are the main advantages of Java 8 features?
- Java 8 will allow you code that is compact, readable, and reusable.
- There will be less boilerplate code.
- The code may be ported to the operating system if it is written using the Java 8 capability.
What is a lambda expression?
Lambda expression is a type of anonymous function which is… Click Here to Learn
What are the three main parts of lambda expressions in Java?
- Parameter list
- Lambda arrow operator
- Lambda expression body
What are functional interfaces?
Single Abstract Method (SAM) interface is another name for functional interface. Click Here to Learn
Is it possible for a functional interface to inherit/extend another interface?
Yes, Click Here to Learn
Is it necessary to use the @FunctionalInterface annotation in Java 8 to establish a functional interface?
No, using the @FunctionalInterface annotation to mark a functional interface is not mandatory.
What is default method in java?
The default method is one that includes a portion of the body. And the default keyword is used to declare this method.
You can provide default implementation if you use the default approach. You may also use the default approach to keep backward compatibility with existing interface-implementing classes.
public interface Car {
public void start();
default void hasAC() {
System.out.println("Has AC");
}
}
In Java, can we override default methods?
Yes, If required, default methods can be overridden in the implementation.
How do you create a functional interface?
Click Here to learn about functional interface.
What are the characteristics of Lambda Expression in Java 8?
- Lambda expressions can be passed to another method as parameters.
- Lambda expressions can be used independent of any class.
What is the relationship between functional interfaces and lambda expressions?
Lambda expressions and functional interfaces are related by the way lambda expressions are applied to the abstract method of functional interfaces.
What does method reference mean in Java 8?
In Java 8, method references are used to refer to functional interface methods. It’s similar to using lambda expressions but with a shorter syntax.
When compared to a lambda that invokes a specific method, method references are the simplest way to refer to a method. The readability of your code will be improved by using method references.
ClassName::methodName
Double::parseDouble(val) \\ Method reference val -> Double.parseDouble(val); \\ Lambda equivalent
What are the most significant differences between Java 8 and previous versions in terms of interfaces?
In Java 8, you can declare and construct concrete methods with bodies as default methods or static methods in addition to abstract methods in interfaces. This is the most major change in the Java 8 interface.
The Java developer may now easily design and update the interface as a result of this improvement.
What is the advantage of Optional in Java 8?
The main advantage of Optional in Java 8 is that it eliminates null testing and eliminates “NullPointerException” problems at runtime.
What is a Stream in java?
A stream is a sequence of data on which different operations or computations can be performed. A stream does not hold any data permanently; instead, it accepts data from external sources like collections, arrays, and I/O channels.
A stream is intended to make complicated data processing operations easier to write. Because Java stream operations use functional interfaces, it’s perfect for functional programming with lambda expressions. Streams in Java 8 provide both sequential and parallel processing.
What is Nashorn in Java?
Nashorn, a JavaScript processing engine, was introduced in Java 8. It also outperforms earlier versions in terms of runtime performance.
What is StringJoiner?
StringJoiner is a commonly used way for creating a string with a certain delimiter. StringJoiner allows us to join together sequences of various characters separated by delimiters.
StringJoiner joiner = new StringJoiner(".");
joiner.add("com").add("util");
System.out.println(joiner); // Displays com.util
What Is JJS in Java 8?
In Java, JJS is a command line tool, or we can say JJS is a new executable tool, that is used to run javascript code on the console.
In Java 8, what is the difference between Predicate, Supplier, and Consumer?
Supplier is an anonymous function that returns a result and takes no arguments. Consumer is an anonymous function that takes an argument and doesn’t return anything.
The predicate, on the other hand, is distinct from the provider and the customer. A predicate is a function with no name that takes an argument and returns a result.
What are the most often used annotations in Java 8?
The annotations @FunctionalInterface and @Repeatable are the two most commonly used annotations in Java 8.
What are the differences between DoubleSummaryStatistics, IntSummaryStatistics, and LongSummaryStatistics?
All of these are used to calculate statistical data, as the name implies. These are applicable to streams. IntSummaryStatistics collects statistical data for int data types, LongSummaryStatistics collects statistical data for long data types, and DoubleSummaryStatistics collects statistical data for double data types.
What is the difference between final and effective final?
Final refers to a variable or parameter that has been declared using the final keyword. Effective final refers to a variable or parameter whose value does not change after initialization.
List of Java 8 Date and Time APIs.
- LocalDate
- LocalTime
- LocalDateTime
How do I get the current date in java 8?
LocalDate currentDate = LocalDate.now();
System.out.println("Current date: " + currentDate);
How can I get current date in local date?
By using now() method.
How do I print random numbers in Java 8?
Random random = new Random(); random.ints().limit(10).forEach(System.out::println);
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