This is an advanced Java interview question and answering it can establish your expertise. Java supports primitive data types such as boolean, int, byte, long, float, etc. An object-oriented language must only support objects. However, the primitive data types are not objects, hence Java is not considered to be purely object-oriented.

Explain the LinkedList class.

There is no ‘virtual’ keyword in Java like in C++. An instance method requires an object of the class to call or invoke it. Therefore, they belong to the object of the class and not the class itself. The JVM (Java Virtual Machine) is the interpreter and is the core of both JDK and JRE. The JVM verifies and executes the program line by line once the program is converted into Bytecode. Memory area, execution engine, JNI, and Native method libraries.

What will be the initial value of an object reference which is defined as an instance variable?

A student will have an address, but it’s not true vice-versa. That means an address does not need to have a student. A base class is also called the parent class, from which the other classes derive. A derived class or the child class inherits properties or functions from the base class.

Question 5: Can you write a critical section code for the singleton? (answer)

One thing you must note is Object clone() is a protected method, thus you need to override it. Synchronized keyword can be applied to java interview questions for senior developer static/non-static methods or a block of code. Synchronized keyword provides a lock on the object and thus prevents race condition.

What is Abstract class?

Once an object has created, there is no need for any synchronization. That’s very poor coding in terms of performance, as synchronized methods reduce production up to 10 to 20 times. Now, as part of the equals-hashcode contract in Java, when you override equals, you must override hashcode as well; otherwise, your object will not break invariant of classes, e.g. Set, Map which relies on equals() method for functioning correctly. This question was mainly asked to see if the developer is familiar with the risk of memory leak, which sub-string can create.

For the technical part of the interview, these 19 Core Java interview questions for experienced talent are ideal for testing their knowledge. Ask them some of these questions to assess your candidates’ expertise. There are also many interview questions which will help students to get placed in the companies. No, we cannot declare an interface as final because the interface must be implemented by some class to provide its definition. Therefore, there is no sense to make an interface final. However, if you try to do so, the compiler will show an error.

What do you get in the Java download file? How do they differ from one another?

The final variable which is not assigned to any value can only be assigned through the class constructor. No, you can’t override the static method because they are the part of the class, not the object. As we know, that this refers to the current class object, therefore, it must be similar to the current class object. However, there can be two main advantages of passing this into a method instead of the current class object.

If you want to execute any java program, you should have JRE installed. The operating system divides the CPU time that is available when numerous threads are running on a single CPU into small time slices and gives each thread a time slice to execute. Rapid switching between the threads by the operating system creates the appearance of parallel execution. The switching between threads appears to be immediate because the time slices are often very tiny, on the order of milliseconds or microseconds. It is mainly used to assign names to integral constants, the names make a program easy to read and maintain.

It is implemented to sort instances of third-party classes. ArrayLists Use more memory due to maintaining the array size. It is to sort and synchronize the collection elements.

So, instead of inheritance, the aggregation is based on the usage of the classes. A try-catch block in Java is responsible for this. The code that may throw exceptions has to be written inside the try block, and if any exception occurs, catch it and work on it in the corresponding catch block.

  1. It is invoked when the class is instantiated, and the memory is allocated for the object.
  2. In these situations, it’s better to use an iterative method or enhance the recursion with memoization to improve efficiency.
  3. Constructor is called during the initialization of objects.
  4. One of the major applications of wrapper classes is changing the value inside the methods.
  5. We can also use this keyword to invoke other constructors from a constructor.

It’s a machine that creates the environment in which Java bytecode can function properly. It’s the main tool in Java used to compile the programs of this language. Within the package, it contains all of the necessary tools to start using it.

You can set the scope of a Spring bean using the `@Scope` annotation or the XML configuration. You should use execute() method only when you are not sure about the type of statement else use executeQuery or executeUpdate method. The ResultSet object represents a row of a table. It can be used to change the cursor pointer and get the information from the database. – Supporting integration with external libraries or frameworks that recognize and operate on marker interfaces.

The above interface has a static method and a default method that can be executed without affecting the class that implements it. However, there is no use in creating the static methods in the Java interface as we cannot override the function by redefining it in the main() method. Polymorphism refers to the ability of objects of different classes to be regarded as objects of a common superclass when writing object-oriented programs.