Hello friends, I have written several OOP (Object Oriented Programming) concepts tutorials in past and I was thinking to bring them together so that anyone who wants to learn OOP basics can benefit from them easily. In this article, I will share with you my collection of OOP tutorials and OOP concepts interview questions, which will not only help you to understand four pillars of Object-Oriented programming like Abstraction, Encapsulation, Inheritance, and Polymorphism but also powerful design techniques of Aggregation, Association, and Composition, along with SOLID design principles, which are key to write flexible, extensible and object-oriented software.
Top 30 OOP (Object Oriented Programming) Interview Questions Answers in Java
Java is an object-oriented programming language and you will see a lot of object-oriented programming concept questions in Java interviews. The classic questions like the difference between an interface and abstract class are always there but from the last couple of years more sophisticated questions based upon advanced design principles and patterns are also asked to check the OOP knowledge of the candidate. Though, Object-oriented programming questions are more popular on Java interviews for 1 to 3 years experienced programmers.
Top 6 Free Object-Oriented Programming Courses for Java Programmers in 2025 [UPDATED]
The OOP or Object Oriented Programming paradigm allows you to write a program by modeling real-world things in terms of class and object. It makes representing a real-world thing in the programming world smoother and will enable you to manage the complexity of your program. Even though several programming paradigms, like procedural and functional, most of the code we write today is object-oriented. Some of the most popular programming languages are object-oriented, like Java, Python, PHP, and JavaScript, all supported object-oriented programming.
Top 5 Courses to learn UML for Software Design and Development in 2025 - Best of Lot
Hello friends, we are here again today for another exciting topic to discuss. But, today we are not gonna discuss something which is related to Java or any other language or spring boot. Today we are gonna discuss something which is immensely practical and very important skill if you want to grow as programmer and become a tech lead or Software architecture. Yes, you guessed it right, today we are going to talk about UML (Unified Modeling Language). Modeling is a process to communicate your design which is in your mind to other people in your team like developers, architect via diagram. This is one of the most important skill if you want to become Software architect in 2025.
Difference between Static and Dynamic binding in Java
Hello guys, if you are wondering what is difference between static and dynamic binding and how it affect your program execution in Java then you are at right place. When you call a method in Java, it is resolved either at compile time or at runtime, depending upon whether it's a virtual method or a static method. When a method call is resolved at compile time, it is known as static binding, while if method invocation is resolved at runtime, it is known as Dynamic binding or Late binding. Since Java is an object-oriented programming language and by virtue of that it supports Polymorphism. Because of polymorphism, a reference variable of type Parent can hold an object of type Child, which extends Parent.
Can You Override static method in Java? Method Hiding Example
Can we
override the static method in Java?
This is one of the most popular Java interview questions. The answer to this question is No, you cannot override the static method in Java because the method
overriding is based upon dynamic binding at runtime and static methods are
bonded using static
binding at compile time. This means static methods are resolved even before objects are created, that's why it's not possible to override static methods in Java. Though you can declare a method with the same name and
method signature in the subclass which does look like you can override static
methods in Java but in reality that is method hiding.
Polymorphism and Open Closed Design Principle Example in Java
Java is an object-oriented programming language that allows developers to create complex software applications by organizing code into objects. One of the key features of object-oriented programming is Polymorphism. Polymorphism refers to the ability of objects to take on different forms, depending on the context in which they are used. In Java, polymorphism is achieved through two mechanisms: inheritance and interfaces. In this blog post, I will explain what polymorphism is in Java, how it works, and provide examples to illustrate its usage. We will also discuss the benefits of using polymorphism in your Java programs, as well as some best practices for implementing it effectively.
Difference between Method and Constructor in Java and OOP? Example
What is the difference between method and constructor in Java is a very common question in beginner-level Java interviews with 2 to 3-year experience. Since the constructor is kind of special and it has its own properties that separate it from any normal Java method, this question makes sense. The main difference between a Constructor and a Method is that you need to call the method explicitly but the constructor is called implicitly by the Java programming language during object instantiation. This is one of the special properties of constructors in Java and that's why all the object initialization code is put inside the constructor.
What is static in Java? Example Tutorial
What is static in Java
Static in Java is related to class if a field is static means it belongs to the class, similarly static method belongs to classes and you can access both static method and field using the class name, for example, if count field is static in Counter class than you can access it as Counter.count, of course, subject to restriction applied by access modifier like private fields are only accessible in class on which they are declared, protected fields are accessible to all classes in the same package but only accessible in subclass outside the package, you can further see private vs protected vs public for complete details on access modifier.
Static in Java is related to class if a field is static means it belongs to the class, similarly static method belongs to classes and you can access both static method and field using the class name, for example, if count field is static in Counter class than you can access it as Counter.count, of course, subject to restriction applied by access modifier like private fields are only accessible in class on which they are declared, protected fields are accessible to all classes in the same package but only accessible in subclass outside the package, you can further see private vs protected vs public for complete details on access modifier.
Can you make an Abstract Class or Method Final in Java? Example
No, you cannot make an abstract class or method final in Java because the abstract and final are mutually exclusive concepts. An abstract class is incomplete and can only be instantiated by extending a concrete class and implementing all abstract methods, while a final class is considered complete and cannot be extended further. This means when you make an abstract class final, it cannot be extended hence it cannot be used and that's why the Java compiler throws a compile-time error when you try to make an abstract class final in Java. In short, an abstract class cannot be final in Java, using both abstract and final modifiers with a class is illegal in Java.
What is Variable and Method Hiding in Java - Example Tutorial
If Java, if you are not careful you can possibly hide both methods and variables of the superclass. Now you must be wondering what does it mean by hiding a variable or method in Java? A field or variable is said to hide all fields with the same name in superclasses. Similarly, a static method with the same name in a subclass can hide the method of the superclass. This can lead to subtle bugs, especially if you are expecting a different method to be called. In this article, I'll show you examples of both variables and methods hiding in Java so that you can understand and avoid them in the future. Earlier, I also wrote about difference between overloading, overriding, shadowing, and hiding, it's a comprehensive post and I suggest you to read it as well if you haven't read already. It will help you to understand these concepts in more detail.
Difference between Abstract class and Interface in Java 8? Answer
Ever since JDK 8 has allowed concrete (non-abstract) methods on the interface like default and static methods, many of my readers have asked me how should they answer the classical abstract class vs interface questions. Earlier, an interface cannot have any concrete methods and that was the main difference between abstract class and interface but now that is not the case. In this post, I'll revisit this hugely popular Java interview question in light of Java 8 changes. This is also a popular Java interview question and knowing the difference will help you to answer this question in a real interview.
Java Interface Example Tutorial
Hello guys, if you are wondering what Java interface is and how to do your user interface in Java, you have come to the right place. Earlier, I have written about the actual use of the interface in Java, and in this article, I will give you an example of an interface in Java. I will also explain what an interface is and how and where you should use it. An interface is nothing but a name. As Joshua Bloch advised in the Effective Java book, the interface is great for declaring type. So, if you want to declare your own type like Employee, Order, Listener, etc., you can use the interface.
How Constructor Chaining works in Java - Example
How to call one constructor from another constructor in Java or What is Constructor Chaining in Java is one of the tricky questions in Java interviews. Well, you can use this keyword to call one constructor from another constructor of the same class if you want to call a constructor from a based class or super class then you can use the super keyword. Calling one constructor from another is called Constructor chaining in Java. Constructors can call each other automatically or explicitly using this() and super() keywords. this() denotes a no-argument constructor of the same class and super() denotes a no argument or default constructor of the parent class. Also having multiple constructors in the same class is known as constructor overloading in Java.
5 Rules of Method Overloading and Overriding in Java? Examples
Since you can either overload or override methods in Java, it's important to know what are the rules of overloading and overriding in Java. any overloaded method or overridden method must follow rules of method overloading and method overriding to avoid compile-time error and logical runtime errors; where you intend to override a method but the method gets overloaded. That is not uncommon and happens several times when a Java programmer tries to override equals in Java or overriding the compareTo method in Java while implementing a Comparable interface, which accepts the Object type of argument.
Difference between Method Overloading and Overriding in Java? Answer
Overloading vs Overriding in Java
In the last couple of articles, we have seen What is method overloading and What is method overriding in Java and now we will see What is difference between overloading and overriding in Java. Overloading vs overriding is one of those frequently asked Java interview questions which can not be ignored. Overloading vs Overriding has appeared in almost every Java interview, mostly at beginner and intermediate level like 2 to 4 years experience. In fact, most of those tricky Java interview Questions came from Overloading and Overriding.
In the last couple of articles, we have seen What is method overloading and What is method overriding in Java and now we will see What is difference between overloading and overriding in Java. Overloading vs overriding is one of those frequently asked Java interview questions which can not be ignored. Overloading vs Overriding has appeared in almost every Java interview, mostly at beginner and intermediate level like 2 to 4 years experience. In fact, most of those tricky Java interview Questions came from Overloading and Overriding.
Can You Override Private Method in Java ? Example
No, We can not override the private method in Java, just like we can not override the static method in Java. Like static methods, the private method in Java is also bonded during compile time using static binding by Type information and doesn't depend on what kind of object a particular reference variable is holding. Since method overriding works on dynamic binding, it's not possible to override the private method in Java.
Difference between Class and Interface in Java and OOP? (with Example)
It is one of the frequently asked Java questions from beginners who struggle to get the concept behind an interface. The main difference between a class and an interface lies in their usage and capabilities. An interface is the purest form of abstraction available in Java where you just define the API or contract e.g. you define run() method on the Runnable interface without worrying about how something will run, that is left to the implementor which will use a class to define how exactly to run. So an interface gives you a method name but how the behavior of that method has come from the class which implements it.
Difference between Static binding vs Dynamic binding in Java? [Answer]
In order to understand the difference between static and dynamic binding in Java, it's important to first learn what is binding? Binding means the link between reference and actual code e.g. when you refer a variable it's bonded to the code where it is defined, similarly when you call a method, it's linked to the code where a method is defined. There are two types of method binding in Java, static binding and dynamic binding. When a method is called in Java it's bonded to the actual code either at compile time or runtime, when the program is actually started and objects are created.
What is Inheritance in Java with example - Object Oriented Programming Tutorial
What is Inheritance in Java
Inheritance in Java or OOPS (Object-oriented programming) is a feature that allows coding reusability. In other words, Inheritance self-implies inheriting or we can say acquiring something from others. Along with Abstraction, Encapsulation, and Polymorphism, Inheritance forms the backbone of Object-oriented programming and Java. In Java, we use the term inheritance when one object acquires some property from other objects. In Java, inheritance is defined in terms of superclass and subclass. it is normally used when some object wants to use an existing feature of some class and also wants to provide some special feature, so we can say inheritance has given the advantage of reusability.
Inheritance in Java or OOPS (Object-oriented programming) is a feature that allows coding reusability. In other words, Inheritance self-implies inheriting or we can say acquiring something from others. Along with Abstraction, Encapsulation, and Polymorphism, Inheritance forms the backbone of Object-oriented programming and Java. In Java, we use the term inheritance when one object acquires some property from other objects. In Java, inheritance is defined in terms of superclass and subclass. it is normally used when some object wants to use an existing feature of some class and also wants to provide some special feature, so we can say inheritance has given the advantage of reusability.
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