10+ Bukeepers Inc Interview Questions and Answers

MongoDB is a NoSQL database while MySQL is a relational database management system.

• MongoDB is schema-less, allowing for flexible data models, while MySQL requires a predefined schema.

• MongoDB uses a document-based data model, storing data in JSON-like documents, while MySQL uses tables with rows and columns.

• MongoDB is better suited for handling unstructured or semi-structured data, while MySQL is ideal for structured data with complex relationships.

• MongoDB is horizontally scal...read more

The new operator is used to create an instance of a class or to allocate memory for an object.

• The new operator is followed by the name of the class and parentheses.

• It can also be used to create arrays of objects.

• Example: MyClass obj = new MyClass();

• Example: int[] arr = new int[5];

JVM stands for Java Virtual Machine. It is an abstract machine that provides a runtime environment for Java programs.

• JVM interprets compiled Java code and executes it

• It provides platform independence by converting bytecode to machine-specific code

• JVM manages memory allocation and garbage collection

• Examples of JVM implementations include Oracle JVM, OpenJDK, and IBM JVM

The new keyword in C++ is used to dynamically allocate memory for an object or array.

• Used to create objects on the heap: MyClass* obj = new MyClass();

• Used to create arrays on the heap: int* arr = new int[10];

JRE stands for Java Runtime Environment. It is a software package that provides the necessary runtime environment for Java applications.

• JRE includes the Java Virtual Machine (JVM), class libraries, and other necessary components to run Java applications.

• It is required to run Java applications on a computer.

• JRE is available for different operating systems such as Windows, Linux, and macOS.

• Examples of Java applications that require JRE include Eclipse, NetBeans, and Apache Tomc...read more

JVM stands for Java Virtual Machine, it is an abstract computing 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 CPU.

• 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 JVM implementations include Oracle HotSpot, OpenJ9, and GraalVM.

Hashmap is a data structure that stores key-value pairs and uses hashing to retrieve values quickly.

• Hashmap uses a hash function to convert the key into an index in an array.

• Collisions can occur when two keys map to the same index, which is resolved using separate chaining or open addressing.

• Hashmap provides constant time complexity O(1) for insertion, deletion, and retrieval of values.

• Java's Hashmap implementation uses an array of linked lists to handle collisions.

• The load f...read more

String is immutable to ensure thread safety and prevent unintended modification.

• Immutable objects are safer to use in multi-threaded environments as they cannot be changed by other threads.

• String pool is possible because of immutability, which saves memory and improves performance.

• StringBuffer and StringBuilder classes are used for mutable string operations.

• Example: String s = "hello"; s.concat(" world"); // returns a new string, s remains unchanged.

List allows duplicate elements and maintains insertion order, while Set does not allow duplicates and does not maintain order.

• List can contain duplicate elements, Set cannot

• List maintains insertion order, Set does not guarantee order

• List is implemented by classes like ArrayList, LinkedList, Set is implemented by classes like HashSet, TreeSet

• Example: List<String> list = new ArrayList<>(); Set<String> set = new HashSet<>();