150+ Core Java Interview Questions and Answers for Freshers and Experienced in 2023

Within the run() method, you must specify the thread’s code. Unchecked exceptions are not checked at compile-time. While exceptions are conditions that occur because of bad input or human error etc. e.g. FileNotFoundException will be thrown if the specified file does not exist.

What this means is that, once a String is created, it stays in the pool in memory until being garbage collected. https://remotemode.net/ Therefore, anyone having access to a memory dump can potentially extract the sensitive data and exploit it.

Java developer Interview Questions

The static method can not use non-static data member or call the non-static method directly. However, we can copy the values from one object to another like copy constructor in C++. Object-oriented languages do not have the inbuilt objects whereas Object-based languages have the inbuilt objects, for example, JavaScript has window object. For example, In the class simulating the collection of the students in a college, the name of the college is the common attribute to all the students. Therefore, the college name will be defined as static. The given print statement will throw a java.lang.NullPointerException because the OR logical operator evaluates both the literals before returning the result. Since str is null, the .equals() method will throw an exception.

Also, it has no return type and it is automatically called when an object is created. In this article, some of the most important Java Interview Questions and Answers are discussed, to give you the cutting edge in your interviews. Java is one of the most popular and widely used programming language and platform. From desktop to web applications, scientific supercomputers to gaming consoles, cell phones to the Internet, Java is used in every nook and corner.

How we can set the spring bean scope. And what supported scopes does it have?

A single teacher can not belong to multiple departments, but if we delete the department teacher object will not destroy. Therefore, Java doesn’t support multiple inheritance. The problem is commonly referred to as Diamond Problem. In Java, super() and this(), both become a java developer are special keywords that are used to call the constructor. When a method is declared final then it can’t be overridden by the inheriting class. As we have synchronized this function, this thread can only use the object after the previous thread has used it.

• For using this driver, Oracle DB, MySQL connector should be installed.
• In C++, default constructor of parent class is automatically called, but if we want to call parameterized constructor of a parent class, we must use Initializer list.
• It has a compiler, Java application launcher, and an applet viewer.
• If this is the case, prepare for both sides of the coin.
• We can declare static methods with same signature in subclass, but it is not considered overriding as there won’t be any run-time polymorphism.
• Therefore, this cannot be assigned to any new value whereas the current class object might not be final and can be changed.

Employers ask candidates specific interview questions in every business. These differ from questions about you to your past work experiences. Make sure to exercise answering these popular questions since they will likely come up in an interview. Recruiters don’t want to scare you and start with serious questions straight away. They will first ask you about some basic stuff, and then go deeper into your knowledge. The final keyword defines the entity which can be assigned only once and can’t be modified in the future.

How do you get the sum of all elements in an integer array in Java?

Moreover, you have to ask yourself the same question before you apply for the job. You’ve probably done a bit of research about the company. Now all you have to do is to adapt your experience and knowledge to their expectations. In java 8, Permgen is replaced by Metaspace, we should be able to answer what advantage it offers.

Default Default are accessible within the package only. By default, all the classes, methods, and variables are of default scope.

This is not only primitives and references are stored but also Objects that has no hope of being referenced outof scope are stored in the Stack Memory. This is efficient because the garbage collector shouldn’t care about local variables that end their lifetime in side the same scope. The finally block always gets executed even hen the return statement is written at the end of the try block and the catch block. It always executes , whether there is an exception or not. There are only a few situations in which the finally block does not execute, such as VM crash, power failure, software crash, etc. If you don’t want to execute the finally block, you need to call the System.exit() method explicitly in the finally block. Connection interface maintains a session with the database.