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Java Interview Questions
Q: What is the difference between a class and a static method?
A: A class defines a group of methods, but a static method can only access private methods in a class. A class can extend other classes and make its methods available to those classes as well. A static method cannot extend a class or any of its methods.
Q: What are the differences between the JVM and HotSpot?
A: The JVM is the programming language. HotSpot is the Virtual Machine.
Q: What is an object-oriented language?
A: An object-oriented language has built-in features that allow it to easily handle the following: abstract classes, inheritance, polymorphism, encapsulation, and multiple inheritance.
Q: Why did the creators of Java create the Java Virtual Machine?
A: They wanted to create a platform on which programmers could write programs that would run on every computer with a processor.
Q: How do you create a method in Java?
A: You need to create an interface and then a class that implements it. Then you can use it in another class.
Q: What is a common error when using static variables?
A: When a static variable is accessed by the same name in multiple classes, it is actually the same static variable, because each class has its own copy of it.
Q: What is object-oriented programming?
A: Object-oriented programming is a way of writing computer programs in which the entities (objects) that make up the application are self-contained. Each entity has its own properties and methods (functions) that can manipulate those properties. Objects interact with each other by sending messages (method calls) to each other.
Q: Describe the benefits of inheritance.
A: With inheritance, you can reuse code and avoid duplication. You can also use different types of variables and data structures.
Q: How does inheritance work?
A: Inheritance allows an object to inherit all of the characteristics of another object. If there is a need to add to the functionality of the base class (the parent), a subclass can create its own class to contain the new behavior.
Q: What are some common OOP pitfalls?
A: Common pitfalls include:
- Not understanding what an abstract class is
- Using too many objects
- Using an OOP framework that does not provide classes for different use cases
Q: What’s the difference between a Java programmer and a Java developer?
A: A Java programmer works with java code and a Java developer uses Java code.
Q: How does an object know which method to call on its class when it receives a method call?
A: When a method call is received, the JVM checks the calling object for a matching method signature. If a match is found, the JVM looks up the method in the class object and executes the method.
Q: What are the differences between object-oriented programming and procedural programming?
A: In object-oriented programming, we create objects and data structures to represent real life. For example, in a restaurant, we would create an object representing a restaurant and we would use this object to access all the restaurant’s information, such as the number of tables, total bill, etc.
In procedural programming, we have no objects.
Other Capgemini Java interview questions
What is JIT compiler?
What is JAR file?
What is classloader?
What is reflection?
How does JVM allocate memory?
What is Garbage Collection?
What is garbage collector?
What is GC pause?
What is thread stack?
What is thread local variable?
What is ThreadLocal?
What is monitor lock?
What is synchronized block?
What is volatile keyword?
What is final keyword?
What is static keyword?
What is object initializer?
What is instance field?
What is static member?
What is final member?
What is inner classes?
What is anonymous class?
What is interface?
What is abstract class?
What is enum?
What is annotation?
What is default method?
What is constructor?
What is static factory method?
What is parameterized type?
What is parameterized Runnable?
What is lambda expression?
What is functional interface?
What is inner class?
What is outer class?
What is static initializer?
What is finalizer?
What is transient keyword?
What is final modifier?
What is volatile keyword?
What is static volatile keyword?
What is package visibility?
What is protected access level?
What is public access level?
What is private access level?
What is protected accessor?
What is static accessor?
What is finalize() method?
What is synchronized method?
What is wait() method?
What is notifyAll() method?
What is interrupt() method?
What is await() method?
What is Object.wait(long) method?
What is ObjectThread.sleep(long) method?
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