10+ Interview Questions and Answers

OOPs concepts in Java include inheritance, polymorphism, encapsulation, and abstraction.

• Inheritance allows a subclass to inherit properties and methods from a superclass.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of an object and only exposes necessary information.

• Abstraction allows for the creation of abstract classes and interfaces that can be implemented by other classes...read more

Overloading is having multiple methods with the same name but different parameters. Overriding is having a method in a subclass with the same name and parameters as a method in the superclass.

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

• Overriding is used to provide a specific implementation of a method in a subclass

• Overloading is resolved at compile-time while overriding is resolved at runtime

• Overloading is used for polymorphism whi...read more

SQL query for joining tables

• Use JOIN keyword to combine two or more tables based on a related column

• Specify the columns to be selected using SELECT keyword

• Use ON keyword to specify the condition for joining the tables

• Different types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN

The == operator compares the memory addresses of two objects, while the equals method compares the content of two objects.

• The == operator is used to compare the memory addresses of two objects in Java.

• The equals method is used to compare the content of two objects in Java.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will return false, but str1.equals(str2) will return true.

Used Java concepts such as inheritance, polymorphism, and exception handling in my project.

• Implemented inheritance to create a base class and derived classes with specific functionalities.

• Utilized polymorphism to allow objects of different classes to be treated as if they were of the same class.

• Implemented exception handling to handle errors and prevent program crashes.

• Used interfaces to define a set of methods that a class must implement.

• Implemented abstract classes to provi...read more

A pointer to pointer is a variable that stores the memory address of another pointer variable.

• It is used to create dynamic data structures like linked lists and trees.

• It allows multiple levels of indirection.

• It is denoted by ** in C and C++.

• Example: int **ptr;

• Example: ptr = &p; where p is a pointer variable.

Main principles of Java include object-oriented programming, platform independence, and automatic memory management.

• Object-oriented programming: Java is based on classes and objects, allowing for encapsulation, inheritance, and polymorphism.

• Platform independence: Java code can run on any platform that has a Java Virtual Machine (JVM) installed.

• Automatic memory management: Java uses garbage collection to automatically manage memory allocation and deallocation.

Interfaces define contracts for behavior, while inheritance allows for code reuse and polymorphism.

• Interfaces allow for loose coupling and abstraction, enabling multiple implementations of the same behavior.

• Inheritance allows for code reuse and extension of existing classes, reducing code duplication.

• Polymorphism allows objects of different classes to be treated as if they were of the same class, simplifying code and increasing flexibility.

Smoke testing is a subset of regression testing that focuses on testing the critical functionalities of an application. Sanity testing is a subset of regression testing that focuses on testing the specific changes made to an application.

• Smoke testing is performed to ensure that the most critical functionalities of an application are working as expected.

• It is usually performed after a build is deployed to check if the application is stable enough for further testing.

• Smoke test...read more

Regression testing is the process of retesting modified software to ensure that the existing functionalities are not affected.

• Regression testing is performed after making changes to the software to ensure that the modifications have not introduced new bugs or issues.

• It involves re-executing previously executed test cases to verify that the existing functionalities still work as expected.

• Regression testing helps in identifying any unintended side effects of code changes and en...read more

Bias is error due to overly simplistic assumptions, variance is error due to overly complex models.

• Bias is the error introduced by approximating a real-world problem, leading to underfitting.

• Variance is the error introduced by modeling the noise in the training data, leading to overfitting.

• High bias can cause a model to miss relevant relationships between features and target variable.

• High variance can cause a model to be overly sensitive to noise in the training data.

• Balancin...read more

Parametric models make strong assumptions about the form of the underlying data distribution, while non-parametric models do not.

• Parametric models have a fixed number of parameters, while non-parametric models have a flexible number of parameters.

• Parametric models are simpler and easier to interpret, while non-parametric models are more flexible and can capture complex patterns in data.

• Examples of parametric models include linear regression and logistic regression, while exam...read more