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Do you like to switch your career? Here's our recommendation on the important things to need to prepare for the job interview to achieve your career goals in an easy way. Java Inheritance is an important pillar of OOP (Object Oriented Programming). It is the mechanism in java by which one class is allowed to inherit the features (fields and methods) of another class. The subclass can add its own fields and methods in addition to the superclass fields and methods. One can check the availability of the job across cities including Mumbai, Delhi, Bangalore, Pune and Hyderabad. Follow Wisdomjobs page for Java Inheritance job interview questions and answers page to get through your job interview successfully in first attempt.
Inheritance is an Object oriented feature which allows a class to inherit behavior and data from other class. For example, a class Car can extend basic feature of Vehicle class by using Inheritance. One of the most intuitive examples of Inheritance in the real world is Father-Son relationship, where Son inherit Father's property. If you don't know, Inheritance is the quick way to become rich.
Java is introduced after C++ and Java designer didn't want to take some C++ feature which is confusing and not essential. They think multiple inheritances is one of them which doesn't justify complexity and confusion it introduces. You can also check why multiple inheritances are not supported in Java for more reasons and discussion around this.
Inheritance is used for code reuse and leveraging Polymorphism by creating a type hierarchy. It's better to use Inheritance for type declaration but for code reuse composition is a better option because it's more flexible. See this article for learning more about why Composition is better than Inheritance.
You can use Inheritance in Java by extending classes and implementing interfaces. Java provides two keywords extends and implements to achieve inheritance. A class which is derived from another class is known as a subclass and an interface which is derived from another interface is called subinterface. A class which implements an interface is known as implementation.
You can use either extends of implements keyword to implement Inheritance in Java. A class extends another class using extends keyword, an interface can extend another interface using extend keyword, and a class can implement an interface using implements keyword in Java.
Inheritance is an object oriented concept which creates a parent-child relationship. It is one of the ways to reuse the code written for parent class but it also forms the basis of Polymorphism. On the other hand, Encapsulation is an object oriented concept which is used to hide the internal details of a class e.g. HashMap encapsulate how to store elements and how to calculate hash values.
Both Polymorphism and Inheritance goes hand on hand, they help each other to achieve their goal. Polymorphism allows flexibility, you can choose which code to run at runtime by overriding. See the detailed answer for more details.
No, you cannot override a static method in Java because it's resolved at compile time. In order for overriding to work, a method should be virtual and resolved at runtime because objects are only available at runtime. This is one of the tricky Java questions, where interviewer tries to confuse you. A programmer is never sure about whether they can override or overload a static method in Java.
Yes, you cannot overload a static method in Java. Overloading has nothing to do with runtime but the signature of each method must be different. In Java, to change the method signature, you must change either number of arguments, type of arguments or order of arguments.
No, you cannot override a private method in Java because the private method is not inherited by the subclass in Java, which is essential for overriding. In fact, a private method is not visible to anyone outside the class and, more importantly, a call to the private method is resolved at compile time by using Type information as opposed to runtime by using the actual object.
Since the static method cannot be overridden in Java, but if you declare the same static method in subclass then that would hide the method from the superclass. It means, if you call that method from subclass then the one in the subclass will be invoked but if you call the same method from superclass then the one in superclass will be invoked. This is known as method hiding in Java.
Yes, A class can implement more than one interface in Java e.g. A class can be both Comparable and Serializable at the same time. This is why the interface should be the best use for defining Type as described in Effective Java. This feature allows one class to play a polymorphic role in the program.
No, a class can only extend just one more class in Java. Through Every class also, by default extend the java.lang.Object class in Java.
Yes, unlike classes, an interface can extend more than one interface in Java. There are several example of this behavior in JDK itself e.g. java.util.List interface extends both Collection and Iterable interface to tell that it is a Collection as well as it allows iteration via Iterator.
In this case, a conflict will arise because the compiler will not able to link a method call due to ambiguity. You will get a compile time error in Java.
Java Inheritance Related Tutorials
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Java Inheritance Related Interview Questions
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An Introduction To Java
The Java Programming Environment
Fundamental Programming Structures In Java
Objects And Classes
Interfaces And Inner Classes
User Interface Components With Swing
Deploying Applications And Applets
Exceptions, Logging, Assertions, And Debugging
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