Ador Digatron Executive - Developer Interview Questions and Answers

finally is used to execute a block of code after try-catch block, while static block is executed when class is loaded.

• finally block is used to perform cleanup operations like closing database connections, file streams etc.

• static block is used to initialize static variables or perform any other static initialization.

• finally block is always executed whether an exception is thrown or not, while static block is executed on...read more

The @Autowired annotation in Spring is used to automatically wire dependencies into a bean.

• It eliminates the need for manual wiring of dependencies

• It can be used to inject dependencies into constructors, fields, and methods

• It can be used with other annotations like @Qualifier and @Value

• It can be used with both XML and Java-based configurations

To make a class immutable in Java, we need to follow certain guidelines.

• Make the class final

• Make all fields private and final

• Do not provide setter methods

• If the field is mutable, return a clone of it instead of the original object

• Ensure that any mutable objects passed to the constructor are not modified outside the class

Collections are data structures that store and manipulate groups of objects.

• Collections provide a way to manage and manipulate groups of objects

• Java provides several built-in collection classes such as ArrayList, LinkedList, HashSet, etc.

• Collections can be used to perform operations like searching, sorting, filtering, etc.

• Collections can store objects of any type, including primitive types and user-defined classes

ArrayList and Vector are similar but Vector is synchronized while HashMap and HashTable are both key-value pair data structures but HashTable is synchronized.

• ArrayList and Vector both implement List interface but Vector is thread-safe while ArrayList is not.

• Vector is slower than ArrayList due to synchronization.

• HashMap and HashTable both store key-value pairs but HashTable is thread-safe while HashMap is not.

• HashMap al...read more

Rest Api is a web service that uses HTTP methods to access and manipulate data.

• Rest stands for Representational State Transfer

• It is an architectural style for building web services

• Uses HTTP methods like GET, POST, PUT, DELETE

• Data is transferred in JSON or XML format

• Examples: Twitter API, Facebook Graph API

Program to add numbers in harmonic series (1+1/2+1/3+...+1/n)

• Create a variable to store the sum

• Use a loop to iterate through the series up to n

• Add each term to the sum

• Print the sum

Dependency injection is a design pattern that allows objects to receive dependencies rather than creating them.

• It helps to decouple the code and makes it more testable and maintainable.

• It allows for easier swapping of dependencies without changing the code.

• There are three types of dependency injection: constructor injection, setter injection, and interface injection.

• Example: Instead of creating a database connection ob...read more

Bean factory is used for creating and managing instances of beans in Spring framework.

• Bean factory is responsible for creating and managing instances of beans defined in the Spring configuration file.

• It provides a way to decouple the configuration and specification of dependencies from the actual application code.

• Bean factory supports different scopes of beans such as singleton, prototype, request, session, etc.

• It also...read more

System.out.println is a Java statement used to print output to the console.

• System is a class in Java's core library.

• out is a static member of the System class.

• println is a method of the PrintStream class.

• It is used to print output to the console.

• It adds a newline character at the end of the output.

Static or final method is a method that belongs to a class rather than an instance of the class.

• Static method can be called without creating an instance of the class.

• Final method cannot be overridden by a subclass.

• Static and final methods can be accessed using the class name.

• Example: Math.max() is a static method in the Math class.

• Example: String.toUpperCase() is a final method in the String class.

A collection is a group of objects that can be stored, manipulated, and retrieved as a single unit.

• Collections are used to store and manage groups of related objects.

• Java provides several built-in collection classes such as ArrayList, LinkedList, HashSet, etc.

• Collections can be used to perform operations like sorting, searching, filtering, and more.

• Collections can be generic or non-generic, depending on the type of obj

Yes, we can add string or integer value using map in Java.

• We can use put() method to add values to a map.

• For string values, we can use String as the value type.

• For integer values, we can use Integer as the value type.

• Example: Map map = new HashMap<>(); map.put("key", "value");

• Example: Map map = new HashMap<>(); map.put("key", 123);

Sleep method pauses the thread for a specified time, while wait method pauses the thread until notified.

• Sleep method is a static method of Thread class, while wait method is an instance method of Object class.

• Sleep method does not release the lock on the object, while wait method releases the lock and waits for notification.

• Sleep method can be interrupted by another thread, while wait method can only be interrupted by ...read more

Join in SQL is used to combine rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables in a single query

• Types of join include inner join, left join, right join, and full outer join

• Join condition is specified using ON keyword

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column

• Join can also be used with subqueries

SQL queries are used to retrieve, manipulate and manage data stored in relational databases.

• SQL stands for Structured Query Language

• Queries can be used to retrieve specific data from tables

• Queries can also be used to update, insert or delete data

• Examples of SQL queries include SELECT, INSERT, UPDATE and DELETE

• Understanding SQL is important for working with databases in Java

Abstraction is a concept of hiding implementation details while interface is a contract that defines the behavior of a class.

• Abstraction is achieved through abstract classes and methods

• Interface is a collection of abstract methods and constants

• Abstraction allows for flexibility in implementation

• Interface allows for multiple inheritance

• Abstraction is used for code reusability

• Interface is used for achieving polymorphism

Overloading is when multiple methods have the same name but different parameters. Overriding is when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading is resolved at compile-time based on the method signature.

• Overriding is resolved at runtime based on the actual object type.

• Overloading is used to provide different ways to call a method with different parameters.

• Overrid...read more

Python interpreter is a program that executes Python code.

• It reads Python code and converts it into machine-readable code

• It executes the code line by line

• It also provides a command-line interface for interactive programming

• Examples: CPython, Jython, IronPython

Python was developed by Guido van Rossum in the late 1980s.

• Guido van Rossum started working on Python in December 1989.

• Python's design philosophy emphasizes code readability and ease of use.

• Python is an interpreted, high-level, general-purpose programming language.

• Python's popularity has been steadily increasing over the years.

• Python is open-source and has a large community of developers contributing to its development

PEP8 is a style guide for Python code.

• PEP8 provides guidelines for formatting, naming, and organizing Python code.

• It covers topics such as indentation, line length, variable naming, and function and class definitions.

• Adhering to PEP8 can improve code readability and maintainability.

• Tools such as Flake8 and PyLint can be used to check code against PEP8 standards.

Python has several built-in data types including integers, floats, strings, booleans, lists, tuples, and dictionaries.

• Integers are whole numbers without decimals

• Floats are numbers with decimals

• Strings are sequences of characters

• Booleans are either True or False

• Lists are ordered collections of items

• Tuples are ordered, immutable collections of items

• Dictionaries are unordered collections of key-value pairs

A class is a blueprint for creating objects that have similar properties and behaviors.

• A class is a user-defined data type that encapsulates data and functions.

• It provides a way to organize and structure code.

• Objects are instances of a class.

• Classes can inherit properties and behaviors from other classes.

• Example: A class 'Car' can have properties like 'color', 'model', and behaviors like 'start', 'stop'.

An object is an instance of a class that encapsulates data and behavior.

• Objects are created from classes

• They have attributes (data) and methods (behavior)

• Objects can interact with each other through method calls

• Examples include a car object with attributes like make, model, and color, and methods like start and stop

• Another example is a person object with attributes like name and age, and methods like walk and talk

Inheritance is a mechanism in object-oriented programming where a new class is created by inheriting properties of an existing class.

• Inheritance allows code reuse and promotes code organization.

• The existing class is called the parent or superclass, and the new class is called the child or subclass.

• The child class inherits all the properties and methods of the parent class and can also add its own unique properties and ...read more

Multiple inheritance is the ability of a class to inherit properties and behavior from multiple parent classes.

• It allows a class to inherit from more than one parent class.

• It can lead to the diamond problem where a class inherits from two classes that have a common base class.

• Languages like C++ support multiple inheritance while others like Java do not.

• Example: A class can inherit properties from both a 'Vehicle' class...read more

Data abstraction is the process of hiding implementation details and showing only the necessary information to the user.

• Abstraction is achieved through abstract classes and interfaces

• It helps in reducing complexity and increasing efficiency

• Example: A car dashboard shows only necessary information like speed, fuel level, etc. and hides the internal workings of the car

• Abstraction is one of the four fundamental concepts o