BPAAS Solutions Interview Questions and Answers

Java is a versatile, object-oriented programming language known for its portability, security, and robust performance.

• Object-Oriented: Java supports encapsulation, inheritance, and polymorphism, allowing for modular and reusable code.

• Platform Independence: Java code is compiled into bytecode, which can run on any device with a Java Virtual Machine (JVM).

• Automatic Memory Management: Java has a built-in garbage coll...read more

The JVM (Java Virtual Machine) is an engine that enables Java bytecode to run on any device, providing platform independence.

• The JVM interprets compiled Java bytecode into machine code for execution.

• It provides memory management through garbage collection.

• JVM allows Java applications to run on any platform with a compatible JVM installed.

• Examples of JVM implementations include HotSpot, OpenJ9, and GraalVM.

Access modifiers in Java control the visibility of classes, methods, and variables, enhancing encapsulation and security.

• 1. Public: Accessible from any other class. Example: public class MyClass {}

• 2. Private: Accessible only within the same class. Example: private int myVar;

• 3. Protected: Accessible within the same package and subclasses. Example: protected void myMethod() {}

• 4. Default (no modifier): Accessible onl...read more

Spring Security is a powerful framework for securing Java applications, providing authentication and authorization features.

• Provides authentication: Verifies user identity through various methods like form login, OAuth, or LDAP.

• Handles authorization: Determines user access levels to resources based on roles or permissions.

• Supports method-level security: Annotations like @PreAuthorize can restrict access to specifi...read more

This function reverses a string represented as an array of characters in place.

• Use two pointers: one at the start and one at the end of the array.

• Swap the characters at these pointers and move them towards the center.

• Continue until the two pointers meet or cross each other.

• Example: Input: ['h', 'e', 'l', 'l', 'o'], Output: ['o', 'l', 'l', 'e', 'h'].

Java 8 introduced significant features like lambdas, streams, and the new Date/Time API, enhancing productivity and code readability.

• Lambda Expressions: Enable concise representation of functional interfaces. Example: (a, b) -> a + b.

• Streams API: Facilitates functional-style operations on collections. Example: list.stream().filter(x -> x > 10).collect(Collectors.toList()).

• Default Methods: Allow interfaces...read more

The final keyword in Java restricts the user from modifying a variable, method, or class, ensuring immutability and preventing overriding.

• Final variables cannot be reassigned after initialization. Example: final int x = 10; x = 20; // Error

• Final methods cannot be overridden by subclasses. Example: final void display() { } in a superclass.

• Final classes cannot be subclassed. Example: final class Constants { } cannot...read more