10 common Core Java Interview Questions & Answers by Yess Infotech

Prepare thoroughly for your Core Java interview with Yess Infotech by revisiting core concepts like OOP principles, data structures, and multithreading. Be ready to showcase your problem-solving skills through coding exercises and discuss real-world Java applications. Additionally, demonstrate your familiarity with commonly used Java frameworks and tools like Spring, Hibernate, and Maven to stand out as a well-rounded candidate.

1. What is the difference between JDK, JRE, and JVM?
   • JDK (Java Development Kit): It is a software development kit that provides the tools and libraries necessary for developing Java applications.
   • JRE (Java Runtime Environment): It is an environment in which Java bytecode can be executed. It includes the JVM and other libraries required to run Java applications.
   • JVM (Java Virtual Machine): It is an abstract machine that provides a runtime environment in which Java bytecode can be executed. It is responsible for interpreting Java bytecode and providing various services like memory management and garbage collection.
2. What are the different types of memory areas allocated by JVM?
   • Heap Memory: It is the runtime data area where objects are stored. It is shared among all threads.
   • Stack Memory: It stores method-specific variables and references to objects in heap memory. Each thread has its own stack memory.
   • Method Area (PermGen/Metaspace): It stores class structures, method and field data, and static variables.
3. What is the difference between == and equals() method in Java?
   • == is used to compare the memory addresses of two objects.
   • equals() method is used to compare the contents of two objects. It is typically overridden by classes to provide custom comparison logic.
4. What is the significance of the static keyword in Java?
   • The static keyword is used to declare members (variables and methods) that belong to the class rather than instances of the class.
   • static members are shared among all instances of the class and can be accessed directly using the class name.
5. What is the difference between ArrayList and LinkedList?
   • ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list.
   • Accessing elements by index is faster in ArrayList, whereas LinkedList provides faster insertion and deletion of elements, especially in the middle of the list.
6. What is the purpose of the finalize() method in Java?
   • The finalize() method is called by the garbage collector before reclaiming the memory occupied by an object that is eligible for garbage collection.
   • Its purpose is to perform any cleanup or resource releasing operations before the object is destroyed.
7. Explain the concept of multithreading in Java.
   • Multithreading allows concurrent execution of multiple threads within a single process.
   • In Java, multithreading is achieved by extending the Thread class or implementing the Runnable interface.
   • Threads share the same memory space and can communicate with each other using synchronization.
8. What are access modifiers in Java?
   • Access modifiers are keywords that specify the accessibility of classes, variables, methods, and constructors.
   • There are four types of access modifiers: public, protected, default (no modifier), and private.
   • They control the visibility of members within the same class, within the same package, and outside the package.
9. What is method overloading and method overriding in Java?
   • Method Overloading: It involves defining multiple methods in a class with the same name but different parameter lists.
   • Method Overriding: It occurs when a subclass provides a specific implementation of a method that is already defined in its superclass. The method signature must remain the same.
10. What is the try-catch-finally block in Java?
    • It is used to handle exceptions in Java.
    • Code that may throw exceptions is placed inside the try block, and corresponding exception handling code is placed inside the catch block.
    • The finally block is optional and is used to execute cleanup code that should run regardless of whether an exception is thrown or not.

Conclusion:
mastering the interview questions and answers for Core Java with Yess Infotech involves a comprehensive understanding of fundamental Java concepts, problem-solving abilities, and familiarity with relevant frameworks and tools. By thoroughly preparing and showcasing your skills and knowledge, you can confidently navigate the interview process and position yourself as a strong candidate for Java development roles within Yess Infotech or any other tech organization.