Worried about potential inheritance questions in your Java interview? No need to stress! Because we have prepared this guide for your help. In Java programming, inheritance plays an important role in code structure and reusability. And, chances are, your interviewer will probe your knowledge on this topic. But are you ready to tackle those questions head-on? Our article covers the top 15+ common inheritance in Java interview questions, providing clear answers.
Understanding these concepts will boost your confidence for any Java interview.
Let’s begin!
Basic Inheritance in Java Interview Questions
Here are some important inheritances in java interview questions and their answers for freshers.
- What is inheritance in Java?
Inheritance in Java is a mechanism where a new class (subclass) can inherit properties and behaviour (methods) from an existing class (superclass).
This makes it easier to reuse code and organize classes in a structured way. By using inheritance, developers can,
- Build upon existing code
- Extend functionality
- Create more specialized classes without duplicating code
- What is the purpose of inheritance?
The main purpose of inheritance is code reuse. It allows classes to inherit commonly used attributes and methods from other classes, reducing redundancy and promoting a modular design.
- What are the types of inheritance in Java?
In Java, there are four types of inheritance:
- Single inheritance (one subclass inherits from one superclass)
- Multilevel inheritance (subclass extends another subclass)
- Hierarchical inheritance (multiple subclasses inherit from one superclass)
- Multiple inheritance (a subclass inherits from multiple superclasses)
- Can a subclass override the methods of its superclass?
Yes, a subclass can override the methods of its superclass. This means it can provide its own implementation for a method inherited from the superclass. This is useful for customizing behaviour in the subclass.
- What is method overriding in Java?
Method overriding in Java occurs when a subclass provides a specific implementation for a method that is already defined in its superclass. The method signature in the subclass must match the method signature in the superclass.
- What is method overloading in Java?
Method overloading in Java occurs when a class has multiple methods with the same name but different parameters. The compiler determines which method to call based on the number and types of arguments passed to it.
Advanced Inheritance Questions in Java
Here are some advanced inheritance in Java interview questions and answers.
- What is the “super” keyword used for in Java?
The “super” keyword in Java refers to the superclass of the current object instance. It can be used to access superclass methods and constructors, as well as to call superclass constructors explicitly from a subclass constructor.
- Can a subclass access private members of its superclass?
No, a subclass cannot directly access the private members of its superclass. Private members are only accessible within the class they are declared in and cannot be inherited by subclasses
- What is a constructor chaining in Java inheritance?
Constructor chaining in Java inheritance refers to the process of calling one constructor from another constructor in a superclass-subclass relationship.
This allows the initialization of inherited members and ensures that all constructors in the inheritance hierarchy are properly invoked.
- Can a subclass inherit from multiple superclasses in Java?
No, Java does not support multiple inheritance, where a subclass inherits from more than one superclass. This is to avoid the “diamond problem”, where ambiguity can arise if two superclasses have methods with the same signature.
- What is the “final” keyword used in inheritance?
In the context of inheritance, the “final” keyword in Java can be used to prevent a class from being subclassed.
It can also be used to prevent methods from being overridden in subclasses, ensuring that the behaviour of a method remains consistent across the inheritance hierarchy.
- What is the diamond problem in inheritance?
The diamond problem in inheritance occurs when a class inherits from two classes that have a common ancestor. This creates ambiguity in method resolution.
In Java, this is resolved using interface inheritance, where a class implements interfaces instead of inheriting multiple classes directly.
Programming Questions on Inheritance in Java
You might also come across programming questions on inheritance in Java. Here are some common ones that interviewers might ask.
- How do you implement inheritance in Java code?
In Java, inheritance is implemented using the “extends” keyword to create a subclass that inherits from a superclass.
For example:
class Subclass extends Superclass {…}.
- How do you prevent a method from being overridden in Java?
You can prevent a method from being overridden by using the “final” keyword in the method signature in the superclass.
For example:
final void methodName() {…}.
- Can a subclass access protected members of its superclass in a different package?
Yes, a subclass in a different package can access protected members of its superclass. Protected members are accessible to subclasses within the same package and to subclasses in different packages.
- Write a Java program to demonstrate constructor chaining in inheritance.
class Superclass {
private int x;
Superclass(int arg) {
this.x = arg;
System.out.println(“Superclass constructor”);
}
}
class Subclass extends Superclass {
private int y;
Subclass(int arg1, int arg2) {
super(arg1);
this.y = arg2;
System.out.println(“Subclass constructor”);
}
public static void main(String[] args) {
Subclass obj = new Subclass();
// Output:
// Superclass constructor
// Subclass constructor
}
}
Inheritance Coding Questions in Java
Here are some important coding-related inheritance in java interview questions and their answers.
- Write a Java program to demonstrate single inheritance.
class Parent {
void display() {
System.out.println(“Parent class method”);
}
}
class Child extends Parent {
public static void main(String[] args) {
Child obj = new Child();
obj.display(); // Output: Parent class method
}
}
- Implement multiple inheritance in Java using interfaces.
interface Interface1 {
void method1();
}
interface Interface2 {
void method2();
}
class MyClass implements Interface1, Interface2 {
public void method1() {
System.out.println(“Method1 implementation”);
}
public void method2() {
System.out.println(“Method2 implementation”);
}
public static void main(String[] args) {
MyClass obj = new MyClass();
obj.method1(); // Output: Method1 implementation
obj.method2(); // Output: Method2 implementation
}
}
- Explain the method hiding in Java inheritance with an example.
Method hiding occurs when a subclass defines a static method with the same name and signature as a static method in the superclass.
For example:
class Parent {
static void display() {
System.out.println(“Parent class method”);
}
}
class Child extends Parent {
static void display() {
System.out.println(“Child class method”);
}
public static void main(String[] args) {
Parent.display(); // Output: Parent class method
Child.display(); // Output: Child class method
}
}
Also Read - Top 25+ Interview Questions On String in Java with Answers
Wrapping Up
And that’s a wrap!
These are the 15+ important inheritance in Java interview questions, along with their answers. Understanding these concepts is key to acing your Java interviews. Ready to kickstart your career in Java development? Visit Hirist to find the best tech job opportunities. Connect with more than 50,000 recruiters, filter job listings and land your dream job with Hirist.
