java object oriented programming interview questions and answers pdf

Java Object Oriented Programming Interview Questions And Answers Pdf

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In this article, we will help you prepare the most crucial OOPs interview questions. Let us review the questions around the key features of OOPs, advantages, and limitations. These OOPs interview questions cover the essential aspects of object-oriented programming.

300 Core Java Interview Questions | Set 1

What are the important features of Java 8 release? If you answer this question clearly, it will show that you like to keep yourself up-to-date with the latest technologies. Java 8 has been one of the biggest releases after Java 5 annotations and generics.

What is the numeric promotion? Answer : Numeric promotions of a numeric operator are used for the conversion of the operands into a common type. In order to perform calculation easily, numeric promotion, conversion is performed. It is the conversion of a smaller numeric type to a larger numeric type so that integer and floating-point operations can be performed over it.

The int values are converted to long values, and the long and float values are converted to double values. What are the methods used to implement for the key Object in the Hash Map?

JIT compiles parts of the bytecode that has similar functionality which in turn reduces the amount of time needed for compilation. Differentiate between a constructor and a method? Can we mark constructors final? Answer: A constructor constructs the value, by providing data for the object. It is a special type of method that is used to initialize the object. The constructor has the same name as the class itself, has no return type, and is invoked using the new operator.

A method is an ordinary member function of a class. A method can be invoked using the dot operator and has its own name, and a return type. No, declaring the constructor as final is not possible. What is the final class? Answer : A final class is a constant value of a final variable. Extending A final class is not possible ie. A final method cannot be overridden when its class is inherited. What is the multi-catch block in Java?

Answer: Multi-catch block makes the code shorter and cleaner when every catch block has a similar code. We can catch multiple exceptions in a single catch block using this feature. What are the important features of Java 10 release? Java 10 is mostly a maintenance release, however, I really liked the local variable type inference feature. What are the important features of Java 9 release?

Public : When a class is public, the public class is visible in other packages, the field is visible everywhere. Private: Private variables or methods can be used by an instance of the same class only which declares the variable or method.

A private feature can be accessed by the class that owns the feature. Protected: Protected variable is available to all classes in the same package. It is also available to all subclasses of the class that owns the protected feature. Subclasses that reside in a different package also is provided with access from the class that owns the protected feature. State the significance of public, private, protected class?

Public: When a class is public, the public class is visible in other packages, the field is visible everywhere. Protected : Protected variable is available to all classes in the same package.

What is JVM and is it platform independent? JVM is responsible for converting byte code into machine-readable code. JDK provides all the tools, executables and binaries required to compile, debug and execute a Java Program. The execution part is handled by JVM to provide machine independence. StringBuilder in Java was introduced in Java 5. What is Enum in Java? Answer: Enum was introduced in Java 1. Enum constants are implicitly static and final. Read more in detail at java enum.

What are Java Annotations? Answer : Java Annotations provide information about the code and they have no direct effect on the code they annotate. Annotations are introduced in Java 5.

Annotation is metadata about the program embedded in the program itself. It can be parsed by the annotation parsing tool or by the compiler.

We can also specify annotation availability to either compile-time only or till runtime also. Read more at java annotations. Answer : Java Reflection API provides the ability to inspect and modify the runtime behavior of java application. We can inspect a java class, interface, enum and get their methods and field details. Reflection API is an advanced topic and we should avoid it in normal programming.

Reflection API usage can break the design pattern such as Singleton pattern by invoking the private constructor i. They invoke the appropriate methods and instantiate classes through reflection API and use it a lot for other processing. What is method overloading and method overriding? Answer: Method Overloading: In Method Overloading, Methods of the same class shares the same name but each method must have a different number of parameters or parameters having different types and order.

It is a compile-time polymorphism. The methods must have a different signature. It may or may not need inheritance in Method Overloading. Online Java Training Courses. What is the difference between path and classpath variables? Answer : PATH is an environment variable used by the operating system to locate the executables. Classpath is specific to Java and used by java executables to locate class files. We can provide the classpath location while running java application and it can be a directory, ZIP files, JAR files, etc.

What is the importance of main method in Java? Answer: main method is the entry point of any standalone java application. The syntax of main method is public static void main String args[]. The input parameter is an array of String through which we can pass runtime arguments to the java program. Check this post to learn how to compile and run a java program. What is the static keyword? Answer: static keyword can be used with class-level variables to make it global i. A static method can access only static variables of class and invoke only static methods of the class.

What is finally and finalize in java? Answer: finally block is used with try-catch to put the code that you want to get executed always, even if an exception is thrown by the try-catch block.

This method gets called by the garbage collector when the object is getting garbage collected. This method is usually overridden to release system resources when object is garbage collected. What is an abstract class? Answer : Abstract classes are used in java to create a class with some default method implementation for subclasses.

An abstract class can have abstract method without body and it can have methods with implementation also. Read important points about abstract classes at java abstract class. What is the difference between Before and BeforeClass annotation? Answer : The code marker Before is executed before each test, while BeforeClass runs once before the entire test fixture.

If your text class has ten tests, Before code will be executed ten times, but BeforeClass will be executed only once. In general, you would use BeforeClass when numerous tests are required to share the same computationally expensive setup code.

Starting a database connection falls into this category. You are able to move code from BeforeClass into Before, but your test run may be delayed. BeforeClass is run as a static initializer, therefore it will run before the class instance of your test fixture is created.

Is it possible to make an array volatile in Java? Answer: Yes, it is possible to make an array volatile in Java, but only the reference which is pointing to an array, not the whole array. Therefore, if one thread changes the reference variable points to another array, which will provide a volatile guarantee. If the purpose is to provide memory visibility guarantee for individual indices of the array, volatile is of no practical use for you.

Instead, you must rely on an alternative mechanism for thread-safety in that particular case, e. From the two, which would be easier to write: synchronization code for ten threads or two threads? Answer : Both will have the same level of complexity regarding writing the code because synchronization is independent of the number of threads, although the choice of synchronization could be subject to the number of threads because this presents more conflict.

Therefore, you would opt for an advanced synchronization technique, e.

Top 30 OOP Concept Interview Questions Answers in Java - Object Oriented Programming

Java Object Oriented Programming 1 - Introduction. Java is selected as the language of choice due to its relatively simple grammars. It is also a good choice for introducing students to the concept of object-oriented programming which is one of the most popular paradigms in the current days. Furthermore, Java is one of the most widely-adopted programming languages by the industries. Object-oriented: Java is based on object-oriented programming where the class and methods describe the state and behavior of an object.

Download PDF We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview questions that an interviewer might ask you during your interview. In this list of Basic Java interview questions, we have covered all commonly asked basic and advanced Core Java interview questions with detailed answers to help you clear the job interview. The following list contains important Core Java interview questions for freshers as well as Java interview questions and answers for experienced programmers to help them prepare for the interview. This detailed guide of interview questions for Java Programming will help you to crack your Job interview easily. What is the difference between an Inner Class and a Sub-Class? Ans: An Inner class is a class which is nested within another class. An Inner class has access rights for the class which is nesting it and it can access all variables and methods defined in the outer class.

OOP is, by far, the most common programming paradigm used in the IT industry. All the major programming languages now support OOP including C. OOP reflects the real world behavior of how things work and the most efficient way to model and organize very large applications. Inheritance allows us to define a class in terms of another class, which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and speeds up implementation time. When creating a class, instead of writing completely new data members and member functions, the programmer can designate that the new class should inherit the members of an existing class. This existing class is called the base class, and the new class is referred to as the derived class.


Java Interview Questions. 1 / Chapter 1. Object Oriented Programming (OOP). Java is a computer programming language that is concurrent, class-based and.


40 Advanced OOP Interview Questions and Answers [2019 Update]

Skip to main content. Search form Search. Java interview bits. Java interview bits java interview bits When we try to restart the same thread as in the below example, we will get IllegalThreadStateException when it executes the second start method of the same thread. What do you mean by an object?

What are the important features of Java 8 release? If you answer this question clearly, it will show that you like to keep yourself up-to-date with the latest technologies. Java 8 has been one of the biggest releases after Java 5 annotations and generics.

Object Oriented Programming (Interview Questions & Answers)

There is the list of core Java interview questions.

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Top 100 Java Interview Questions and Answers (Download PDF)

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Ans: Encapsulation is a concept in Object Oriented Programming for combining properties and methods in a single unit. Encapsulation helps.

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