Reactive programming enables developers to write code that is more concurrent and asynchronous. By using reactive streams and operators, developers can create pipelines of data processing that can run in parallel, without the need for manual synchronization or locking. In Java, constructor refers to a block of code which is used to initialize an object.

Beans are objects that form the backbone of a Spring application. In other words, a bean is an object that is instantiated, assembled, and managed by a Spring IoC container. Wikipedia defines the Spring framework as “an application framework and inversion of control container for the Java platform. Statement executeQuery(String query) is used to execute Select queries and returns the ResultSet.

Finalize is used to call the function of the implementation of cleaning the garbage collection of an object. Java Cryptography Architecture gives a platform and provides architecture and application programming interfaces that enable decryption and encryption. Spring is essentially defined as an application framework in Java and inversion of control containers for Java.

Java Coding Interview Questions: Answers and Explanations

An immutable object is one that cannot change after it’s constructive. However, Java developers are sometimes reluctant to use immutable objects if they need to account for updates down the line. In case you are facing any challenges with these Core Java interview questions, please comment on your problems in the section below.

• Especially after java 8 changes where there are major updates regarding it.
• It means we’ll create only one instance of that static member that is shared across all instances of the class.
• To convert a Java object to JSON, you can use a JSON library such as Jackson or Gson.
• Some popular libraries for implementing reactive programming in Java include RxJava, Reactor, and Akka Streams.

Project Reactor provides built-in support for testing reactive streams. The StepVerifier class allows developers to test the behavior of a reactive stream by defining a sequence of expected events and verifying that the actual events match the expected events. The StepVerifier class also provides operators for testing error handling, backpressure, and multi-threading.

Can Java be said to be the complete object-oriented programming language

It can only throw one exception at a time whereas throws can be used to declare multiple exceptions. An abstract class can have a combination of both abstract and non-abstract methods, whereas an interface has only abstract methods in it. Finally is used to execute the code written inside the block without handling any exceptions.

If available, the same object reference is shared with the variable, else a new object is created. In Java, Strings are immutable and are stored in the String pool. What this means is that, once a String is created, it stays in the pool in memory until being garbage collected. Therefore, anyone having access to a memory dump can potentially extract the sensitive data and exploit it. With these behavioral interview questions, you can determine whether the candidate was a team player who worked well with others. You’ll also learn how they prioritize tasks and describe what they would do differently.

However, we can also make objects eligible for garbage collection manually using the System.gc() method or by setting the object reference to null. One of the main differences between instance variables and local variables is their scope. The second difference between instance variables and local variables is their initialization.

Can static methods be overridden?

In case you are facing any challenges with these java interview questions, please comment on your problems in the section below. In Java, string objects are immutable in nature which simply means once the String object is created its state cannot be modified. Whenever you try to update the value of that object instead of updating the values of that particular object, Java creates a new string object.

In Java, object variables always refer to the memory heap’s real object. This creates a thread by creating an instance of a new class that extends the Thread class. The extending class must override the run() function, which is the thread’s entry point. Hibernate has a layered architecture which helps the user to operate without having to know the underlying APIs. Hibernate makes use of the database and configuration data to provide persistence services (and persistent objects) to the application.

The Non-Serialized attribute can be used to prevent member variables from being serialized. You should also make an object that potentially contains security-sensitive data non-serializable if possible. Apply the Non-Serialized attribute to certain fields that store sensitive data if the object must be serialized. If you don’t exclude these fields from serialization, the data they store will be visible to any programs with serialization permission. When you create a subclass instance, you’re also creating an instance of the parent class, which is referenced to by the super reference variable.

Big list, almost cover all topics required for Java interviews. Good Job Javin, keep it up, you are inspiration for many Java developers. Particularly 89 – you do not need any mocking library to test a static method – just write a test for it. This question reveals the senior developer’s experience with different SDLC practices. The try…catch block in Java is for handling exceptions and preventing abnormal program termination.

Senior Java Developer Interview Questions (With Example Answers)

The FailFast iterators tend to fail and throw an exception called ConcurrentModificationException. The Observer interface gets implemented by objects that observe Observable objects. No, the thread might release the locks using notify, notifyAll(), and wait() methods. Since this char [] array is used by the Java String class internally, the length variable cannot be made public.

JVM has a Just in Time (JIT) compiler tool that converts all the Java source code into the low-level compatible machine language. The prototype scope creates a new instance of a bean for each object that requests it. The third object is created when the user inputs their address and is no longer needed when the program ends. The second object is created when the user inputs their name and is no longer required when the program ends. The first object is created when the program is started and is no longer needed when the program ends.

• It can tell you exactly how much the applicant understands about when to choose a specific database architecture and which database to choose for a specific situation.
• Some examples of Structural patterns are Adapters, bridges, and Composites.
• Java is called platform independent because of its byte codes which can run on any system irrespective of its underlying operating system.
• As a result, when the final product is completed, it will be error-free.
• In this code, we declare an array of size five and assign values to each element.
• On the other side, executing tD.setDaemon(false) would convert a Daemon thread, tD, into a user thread.

The first add() method accepts a single argument of type E, the element to be added to the list. This technique designates whether the active thread is a user thread or a daemon thread. For instance, tU.setDaemon(true) would convert a user thread named tU into a daemon thread. On the other side, executing tD.setDaemon(false) would convert a Daemon thread, tD, into a user thread. Java Virtual Machine takes care of memory management implicitly.

The Waiting state represents a thread that is waiting for another thread to perform a specific action. The Timed Waiting state represents a thread that is waiting for a specific amount of time to elapse. The Terminated state represents a thread that has completed its execution. Shallow copy and deep copy are two types of object copying in Java. SC creates a new object with the same values as the original object, while deep copy creates a new object with new values. The covariant return type is a feature introduced in Java 5 that allows a subclass method to return a type that is a subclass of the return type of the overridden method in the superclass.

The ResultSetMetaData interface returns the information of table such as total number of columns, column name, column type etc. It can be used to change the cursor pointer and get the information from the database. Composition is again a specialized form of Aggregation and we can call this as a “death” relationship. Child object does not have their lifecycle and if parent object deletes all child object will also be deleted.

It includes many objects such as persistent object, session factory, transaction factory, connection factory, session, transaction etc. We can define exception handler methods in our controller classes. All we https://trading-market.org/ need is to annotate these methods with @ExceptionHandler annotation. JDBC statements are basically the statements which are used to send SQL commands to the database and retrieve data back from the database.

The synchronized keyword in Java is used to identify synchronized blocks. In Java, a synchronized block is one that is tied to an java interview questions for senior developer object. Only one thread can be running at a time inside synchronized blocks since they are all synchronized on the same object.

It is a programming language that is independent of platforms. Java doesn’t demand that the complete programme be rewritten for every possible platform. The Java Virtual Machine and Java Bytecode are used to support platform independence.

Which of them is most efficient for adding and removing elements from the list? Explain your answer, including any other alternatives you may be aware of. Some of the questions have not been answered here, because of the limited time I have. Furthermore, it contains data about bytecode, names, and JIT information.

Spring MVC Framework provides the following ways to help us achieving robust exception handling. ContextLoaderListener, on the other hand, is the listener to start up and shut down the WebApplicationContext in Spring root. Some of its important functions includes tying up the lifecycle of Application Context to the lifecycle of the ServletContext and automating the creation of ApplicationContext. Statement executeUpdate(String query) is used to execute Insert/Update/Delete (DML) statements or DDL statements that returns nothing.