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5 days ago · Prepare for your next Java 8 interview with this list of commonly asked questions and detailed answers. Learn about lambda expressions, stream API, functional interfaces, date and time API, and more.
- Table of Content
- Java 8 Features Interview Questions For Experienced
- Java 8 Interview Questions For 2 to 3 Years of Experience
- Java 8 Features Interview Questions For 4 to 5 Years Experience
- Advanced Java 8 Interview Questions
- Java 8 Interview Questions For 6 to 7 Years of Experience
- Java 8 Interview Questions For 8 to 10 Years of Experience
- Java 8 Interview Questions For 11 to 12 Years of Experience
- Java 8 Coding Interview Questions
- Java 8 Tricky Interview Questions
7. What is the meaning of functional interfaces in Java 8?
Functional interfaces in Java 8 are interfaces having a single abstract method. Following are the three types of methods that can be present: 1. The static method 2. The default method 3. The overridden class method
8. What is the use of the String::ValueOf expression in Java 8?
String::ValueOf is a simple static method referencing the valueOf method, belonging to the class ‘String.’ Next up on this Java8 Interview Questions and Answers post, we have to check out an important concept regarding the interface.
10. What are default methods in Java 8?
Default methods are the interfaces in Java 8 that make use of the ‘default’ keyword. Default methodsare added to Java 8 to give users the functionality and ability to use backward compatibility.
12. Is it possible to create a custom functional interface in Java 8?
Yes, Java 8 supports the creation of a custom functional interface. The following example denotes the creation of an interface called ‘CustInterface’ as shown: The main class can be created as shown below: When the program runs, it prints out the ‘printing form’ message to the screen. It is very vital that youlearn Javawith the programming approach.
13. What is the meaning of method reference in Java 8?
Methodreferences are used in Java 8 to refer to methods of functional interfaces. It can be considered as a short-code version of using a lambda expression. The following is the expression for a method reference:
14. How can you create custom functional interfaces in Java 8?
We can create custom functional interfaces by adding the @FunctionalInterface annotation to any interface with a single abstract method. It can contain default and static methods too. This allows leveraging lambda expressions for desired functionality. For example:
16. What is the easiest way to print the current date and time using the new APIs in Java 8?
The ‘now’ method, which is a part of LocalDate, can be used to get the current date as shown below: Similarly, it can also be used to get the current time:
17. What were the issues that were fixed with the new Date and Time API of Java 8?
With the older versions of Java, java.util.The date was mutable. This means it has absolutely no thread safety. Also, java.text.SimpleDateFormat was not thread-safe in the older versions. The older Date and Time API was difficult to understand for programmers in terms of readability too.
18. What are PermGen and Metaspace in Java 8?
The Java Virtual Machine has been using PermGen for class storage until Java 7. It is now superseded by Metaspace. Metaspace has a huge advantage over PermGen that makes the former grow dynamically without any constraint, while PermGen has a fixed maximum size.
23. What is the use of the peek() method in streams?
peek() allows debugging or logging in pipelinestages without impacting actual stream behavior. It is useful for examining stream content at various pipeline stages, especially in complex transformations.
24. What is Nashorn in Java 8?
Nashorn is a newly introduced JavaScript processing engine that came bundled with Java 8. It provides tighter compliances with ECMA JavaScriptspecifications and has runtime performance that beats Rhino, its predecessor. If you want to know the difference between Python and Javascript, check out the Python vs Javascriptblog!
25. What is the use of the optional keyword in Java 8?
The optional keyword is used in Java 8 to avoid the occurrence of the NullPointerException. An optional object can be created easily using the empty() static method as shown below: If you want to know more about the exception handling, check out the Exception handlingblog
28. What is the code to sort strings using the Java 8 lambda expression?
The below piece of code sorts strings using the lambda expression:
29. Is it possible to call a static method of any interface in a class using Java 8?
Yes, it is possible to call a static method in a class by making use of the name as shown below: Next up in this Blog on Java 8 Interview Questions for the experienced, we have to check out an important concept regarding keywords.
30. Can you briefly explain the working of the random keyword in Java 8?
The random keyword, as the name suggests, is used to generate random values for computations and operations in Java 8. The following piece of code is used to print out 20 random numbers using the forEach loop:
34. What is the easiest way to print the sum of all of the numbers present in a list using Java 8?
In Java 8, the following code is used to print the sum of all of the numbers that are present in a list:
35. Can JavaScript code be executed from Java 8 codebase?
Yes, JavaScriptcode can be easily executed using a codebase by making use of ScriptEngineManger. This is used to interpret the code in Java 8.
36. When is an ideal situation to use the Stream API in Java 8?
The Stream API in Java 8 can be effectively used if the Java project calls for the following operations: 1. Perform databaseoperations 2. Execute operations lazily 3. Write functional-style programming 4. Perform parallel processing 5. Use pipeline operations 6. Use internal iteration
43. What is a supplier in Java 8?
A supplier is a simple functional interface in Java 8 that does not take in any argument. It is used as an assignment target when making use of lambda expressions. The following is an example that denotes the usage of a supplier:
44. What is a consumer in Java 8?
Similar to a predicate, a consumer is a functional interface with a single argument in Java 8. However, unlike a predicate, a consumer does not return any value and is commonly used for lambda expressions. Below is an example code snippet that demonstrates the usage of the consumer interface to print a string: In the given code snippet, there is a consumer named consumerString which accepts a String parameter and prints it using the System.out.println statement. The accept methodis used to pa...
47. What is the meaning of a Spliterator in Java 8?
Spliterator is a newly introduced iterator interface for Java 8. It is very efficient and handles API-related operations seamlessly across the runtime environment.
61. Write a code to sort a List of Strings by their length using Stream API.
This first obtains a Stream from the list of strings. The sorted method applies a custom Comparator implemented using a lambda expression. It compares the lengths of two strings, s1 and s2. Finally, we print each string using Each terminal operation.
62. How to implement a Runnable interface in Java 8 using a lambda expression?
We can implement the run() method of Runnable using a lambda expression as: This implements the functional interface Runnable using lambda, featuring empty args and a run method body inside curly braces. Then we pass the task Runnable to a Thread instance to start execution. If you want to know more about the Java MapReduce, check out the Java MapReduceblog
63. Write code to sum integers in a List using reduce() operator.
The identity element is initialized to 0, and lambdaexpression implements adder logic. This accumulates the sum progressively using reduce.
64. Can we define a static method in a functional interface in Java 8?
Yes, it is perfectly valid to define static methods inside functional interfaces. Since Java 8, interfaces can contain both default and static methods. The single abstract method rule applies only to non-static, non-default methods. Defining static methods allows the interface to provide helper utilities to implementers without needing to inherit a class. If you want to know more about the Inheritance in Java, check out the Inheritance in Javablog
65. Is this Stream pipeline written correctly?
No, the above code has an issue. The stream is first filtered to contain only null names using filter(). Calling toUpperCase on a null String would throw a NullPointerException. The filter should be moved after the map() operation to avoid this scenario.
66. What is the output of the following pipeline operation?
The output of the above pipeline is: The peek() operation prints the stream elements as they pass through the pipeline. Next, limit(3) limits the size of the stream to the first 3 elements. So the stream becomes (1, 1, 3). Now distinct() removes any duplicates and passes on (1, 3) forward. The final forEach prints the distinct elements (1, 3). Because of the interleaved peek, it prints “1113123.” The peek executes before the limit, printing initial elements before truncation.
- Intellipaat
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Jun 26, 2023 · Learn how to answer common Java 8 interview questions with code examples and explanations. Topics include streams, lambdas, functional interfaces, date and time API, and more.
