Xangars Solutions Java Developer Interview Questions and Answers

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.

• Abstract class can have constructors, member variables, and methods, while interface cannot.

• A class can implement multiple interfaces but can only extend one abstract class.

• Abstract classes are used to define a common behavior among subclasses, while interfaces are used to define a contract for classes to impl...read more

Abstract classes can have both implemented and abstract methods, while interfaces can only have abstract methods. Abstract classes support single inheritance, interfaces support multiple inheritance.

• Abstract classes can have both implemented and abstract methods, providing more flexibility in design.

• Interfaces can only have abstract methods, promoting a more strict contract for implementing classes.

• Abstract classes sup...read more

JVM stands for Java Virtual Machine, which is an abstract machine that enables a computer to run Java programs.

• JVM is responsible for converting Java bytecode into machine code that can be executed by the computer's operating system.

• It provides a platform-independent execution environment for Java programs.

• JVM manages memory, handles garbage collection, and provides security features for Java applications.

• Examples of J...read more

Inheritance in JAVA allows a class to inherit properties and behaviors from another class.

• Allows a class to inherit fields and methods from another class

• Promotes code reusability and reduces redundancy

• Creates a parent-child relationship between classes

• Example: class B extends class A

HashMap is not thread-safe and allows null keys/values, while ConcurrentHashMap is thread-safe and does not allow null keys/values.

• HashMap is not thread-safe and can lead to ConcurrentModificationException if modified while iterating.

• ConcurrentHashMap uses internal locking mechanisms to provide thread-safety.

• ConcurrentHashMap does not allow null keys/values, while HashMap does.

• ConcurrentHashMap is more suitable for con

Method overloading is when multiple methods in a class have the same name but different parameters.

• Allows multiple methods with the same name but different parameters in a class

• Parameters can differ in number, type, or order

• Compile-time polymorphism

• Example: void print(int a) and void print(String s)

Method overloading allows defining multiple methods with the same name but different parameters.

• Methods must have different parameter types or number of parameters.

• Return type does not matter for method overloading.

• Example: void print(int num) and void print(String text) are valid overloads.

JVM optimizes method calls using various techniques like inlining, escape analysis, and virtual method resolution.

• JVM can inline methods by replacing the method call with the actual code, reducing overhead.

• Escape analysis helps JVM determine if objects can be allocated on the stack instead of the heap.

• Virtual method resolution optimizes method calls by caching the resolved method to avoid repeated lookups.