Top Java Interview Questions and Answers For Experienced

  1. What do you understand by Java?
    Java is an object-oriented computer language.
    It is a high-level programming language developed by James Gosling in Sun Microsystems in the year 1995.
    Java is a fast, secure, and reliable language used for many games, devices, and applications.
    Go through this Java Tutorial to get a better understanding of the concept!
  2. Compare between Java and Python.
    Criteria Java Python
    Ease of use Good Excellent
    Speed of coding Average Excellent
    Data types Static typed Dynamically typed
    Data Science and Machine Learning applications Average Excellent
  3. Outline the major Java features.
    Object-oriented: Java is based on object-oriented programming where the class and methods describe the state and behavior of an object.
    Portable: A Java program gets converted into Java bytecodes that can be executed on any platform without any dependency.
    Platform independent: Java works on the ‘write once, run anywhere’ principle as it supports multiple platforms like Windows, Linux, Mac, Sun Solaris, etc.
    Robust: Java has strong memory management as there are no pointer allocations. It has an automatic garbage collection that prohibits memory leaks.
    Interpreted: As mentioned, Java compiler converts the codes into Java bytecodes which are then interpreted and executed by Java Interpreter.
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  4. What do you mean by an object?
    An object consists of methods and classes that depict its state and perform operations. A Java program contains a lot of objects instructing each other their jobs. This concept is part of core Java.
  5. What is a class in Java?
    Java encapsulates codes in various classes that define new data types. These new data types are used to create objects.
  6. Differentiate between JDK, JRE, and JVM.
    JVM stands for Java Virtual Machine which provides the runtime environment for Java bytecodes to be executed.
    JRE (Java Runtime Environment) includes the sets of files required by JVM during runtime.
    JDK (Java Development Kit) consists of JRE along with the development tools required to write and execute a program.
    Get a clear idea of why to get certified in Java!
  7. Define inheritance.
    Java includes the feature of inheritance which is an object-oriented programming concept. Inheritance lets a derived class inherit the methods of a base class.
  8. Explain method overloading.
    When a Java program contains more than one method with the same name but with different properties, then it is called method overloading.
  9. Compare overloading with overriding.
    Overloading refers to the case of having two methods of the same name but different properties; whereas, overriding occurs when there are two methods of the same name and properties, but one is in the child class and the other is in the parent class.
    Read this tutorial to get a clear understanding of inheritance in Java!
  10. Explain the creation of a thread-safe singleton in Java using double-checked locking.
    Singleton is created with the double-checked locking as before Java 5 acts as a broker and it’s been possible to have multiple instances of singleton when multiple threads create an instance of the singleton at the same time. Java 5 made it easy to create thread-safe singleton using Enum. Using a volatile variable is essential for the same.

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