Java Questions and Answers for Viva

Answer-1: Primitive types include byte, short, int, long, float, double, char, and boolean.

Answer-2: Method overloading is defining multiple methods with the same name but different parameters.

Answer-3: Method overriding occurs when a subclass provides a specific implementation of a method from its superclass.

Answer-4: The final keyword is used to define constants, prevent method overriding, or inheritance.

Answer-5: A static method belongs to the class rather than an instance of the class.

Answer-6: The hierarchy starts with Throwable, which has two branches: Error and Exception.

Answer-7: Use try, catch, finally, and throw to handle exceptions.

Answer-8: throw is used to explicitly throw an exception; throws declares exceptions in a method signature.

Answer-9: Control statements include if, else, switch, for, while, and do-while.

Answer-10: A thread is a lightweight process in Java for performing concurrent tasks.

Answer-11: Runnable is an interface; Thread is a class. Implementing Runnable is preferred for better flexibility.

Answer-12: Synchronization ensures that only one thread accesses critical sections at a time.

Answer-13: Memory areas include Heap, Stack, Code, and Method Area.

Answer-14: Garbage collection is the process of reclaiming unused memory automatically.

Answer-15: Collections are frameworks like ArrayList, HashMap, and HashSet for managing data structures.

Answer-16: A HashMap is a collection that maps keys to values using hashing.

Answer-17: HashMap is unsynchronized and allows null keys; Hashtable is synchronized and doesn't allow null keys.

Answer-18: The transient keyword prevents serialization of certain fields.

Answer-19: volatile ensures that changes to a variable are visible to all threads.

Answer-20: Functional interfaces have a single abstract method and are used in lambda expressions.

Answer-21: The Stream API allows processing sequences of data with functional programming techniques.

Answer-22: Comparable is used for natural ordering; Comparator is used for custom ordering.

Answer-23: Reflection is the ability to inspect and modify classes, methods, and fields at runtime.

Answer-24: super is used to refer to the immediate parent class.

Answer-25: Polymorphism allows methods to perform differently based on the object that calls them.

Answer-26: Common patterns include Singleton, Factory, Observer, and Strategy.

Answer-27: this refers to the current instance of a class.

Answer-28: A marker interface has no methods and is used for metadata purposes (e.g., Serializable).

Answer-29: Optional is a container object to avoid null and handle values that may be absent.

Answer-30: Streams process elements only when a terminal operation is invoked.

Answer-31: == checks reference equality; .equals() checks value equality of strings.

Answer-32: Use javac .java to compile and java to run the program.

Answer-33: Key features include platform independence, object-oriented programming, robustness, and security.

Answer-34: JVM is the runtime environment in Java that executes Java bytecode.

Answer-35: JRE is the runtime environment that provides libraries and JVM for running Java applications.

Answer-36: JDK is a software development kit that includes tools like the compiler, debugger, and JRE.

Answer-37: JDK includes development tools and JRE; JRE includes libraries and JVM; JVM executes bytecode.

Answer-38: Bytecode is an intermediate code generated after compiling Java source code.

Answer-39: The main() method is the entry point of a Java application.

Answer-40: A ClassLoader is a subsystem of JVM that loads classes and interfaces into memory.

Answer-41: == compares object references, while .equals() compares the actual content of objects.

Answer-42: A constructor is a special method used to initialize objects.

Answer-43: Access modifiers include public, private, protected, and default (no modifier).

Answer-44: ArrayList uses dynamic arrays, while LinkedList uses doubly linked lists.

Answer-45: String is immutable; StringBuilder is mutable and non-synchronized; StringBuffer is synchronized.

Answer-46: An interface is a reference type that contains abstract methods and constants.

Answer-47: An abstract class is a class that cannot be instantiated and may contain abstract methods.

Answer-48: Java doesn't support multiple inheritance with classes, but it does with interfaces.

Answer-49: Java is a high-level, object-oriented programming language designed to have as few implementation dependencies as possible.

Answer-50: Java was developed by James Gosling at Sun Microsystems in 1995.