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Abstraction is a concept of showing only important information and hiding its implementation. This is one of the most asked Oops interview questions as it checks basic oops concepts for java programmers.
- Top 15 OOPS Interview Questions & Answers
- OOPS Interview Questions and Answers
- OOP Interview Questions
Oops is a concept or methodology which is use to write computer programes by using class and object. Oops stands for object oriented programming its a example of programming language which deals with, object and its interaction to develop computer Applications and program. Object Oriented Programming System is a mechanism to write a computer program by using class and Object.
Top 15 OOPS Interview Questions & Answers
There is the list of core Java interview questions. If there is any core Java interview question that has been asked to you, kindly post it in the ask question section. The answers to the Core Java interview questions are short and to the point. The core Java interview questions are categorized in Basics of Java interview questions, OOPs interview questions, String Handling interview questions, Multithreading interview questions, collection interview questions, JDBC interview questions, etc.
Java is the high-level, object-oriented , robust, secure programming language, platform-independent, high performance, Multithreaded, and portable programming language. It was developed by James Gosling in June Java Virtual Machine is a virtual machine that enables the computer to run the Java program.
JVM acts like a run-time engine which calls the main method present in the Java code. JVM is the specification which must be implemented in the computer system. The Java code is compiled by JVM to be a Bytecode which is machine independent and close to the native code. JVM is an acronym for Java Virtual Machine; it is an abstract machine which provides the runtime environment in which Java bytecode can be executed.
It is a specification which specifies the working of Java Virtual Machine. Its implementation has been provided by Oracle and other companies. Its implementation is known as JRE. It is a runtime instance which is created when we run the Java class. There are three notions of the JVM: specification, implementation, and instance.
It is the implementation of JVM. The Java Runtime Environment is a set of software tools which are used for developing Java applications. It is used to provide the runtime environment. It physically exists. It is a software development environment which is used to develop Java applications and applets. JIT compiles parts of the bytecode that have similar functionality at the same time, and hence reduces the amount of time needed for compilation. A platform is the hardware or software environment in which a piece of software is executed.
There are two types of platforms, software-based and hardware-based. Java provides the software-based platform. The bytecode. Java compiler converts the Java programs into the class file Byte Code which is the intermediate language between source code and machine code.
This bytecode is not platform specific and can be executed on any computer. Classloader is a subsystem of JVM which is used to load class files. Whenever we run the java program, it is loaded first by the classloader.
There are three built-in classloaders in Java. Yes, Java allows to save our java file by. The local variables are not initialized to any default value, neither primitives nor object references. In Java, access specifiers are the keywords which are used to define the access scope of the method, class, or a variable. In Java, there are four access specifiers given below.
The methods or variables defined as static are shared among all the objects of the class. The static is the part of the class and not of the object. The static variables are stored in the class area, and we do not need to create the object to access such variables. Therefore, static is used in the case, where we need to define variables or methods which are common to all the objects of the class.
For example, In the class simulating the collection of the students in a college, the name of the college is the common attribute to all the students.
Therefore, the college name will be defined as static. In the first case, 10 and 20 are treated as numbers and added to be Now, their sum 30 is treated as the string and concatenated with the string Javatpoint. Therefore, the output will be 30Javatpoint.
In the second case, the string Javatpoint is concatenated with 10 to be the string Javatpoint10 which will then be concatenated with 20 to be Javatpoint In the first case, The numbers 10 and 20 will be multiplied first and then the result is treated as the string and concatenated with the string Javatpoint to produce the output Javatpoint. In the second case, The numbers 10 and 20 will be multiplied first to be because the precedence of the multiplication is higher than addition.
The result will be treated as the string and concatenated with the string Javatpoint to produce the output as Javatpoint The above code will give the compile-time error because the for loop demands a boolean value in the second part and we are providing an integer value, i. However, they have been categorized in many sections such as constructor interview questions, static interview questions, Inheritance Interview questions, Abstraction interview question, Polymorphism interview questions, etc.
It is a programming paradigm based on objects having data and methods defined in the class to which it belongs. Object-oriented paradigm aims to incorporate the advantages of modularity and reusability.
Objects are the instances of classes which interacts with one another to design applications and programs. There are the following features of the object-oriented paradigm. The Object is the real-time entity having some state and behavior. In Java, Object is an instance of the class having the instance variables as the state of the object and the methods as the behavior of the object.
The object of a class can be created by using the new keyword. There are the following basic differences between the object-oriented language and object-based language. The constructor can be defined as the special type of method that is used to initialize the state of an object.
It is invoked when the class is instantiated, and the memory is allocated for the object. Every time, an object is created using the new keyword, the default constructor of the class is called. The name of the constructor must be similar to the class name. The constructor must not have an explicit return type. The purpose of the default constructor is to assign the default value to the objects. The java compiler creates a default constructor implicitly if there is no constructor in the class.
Explanation: In the above class, you are not creating any constructor, so compiler provides you a default constructor. Here 0 and null values are provided by default constructor. Ans: yes, The constructor implicitly returns the current instance of the class You can't use an explicit return type with the constructor.
More Details. Yes, the constructors can be overloaded by changing the number of arguments accepted by the constructor or by changing the data type of the parameters. Consider the following example. In the above program, The constructor Test is overloaded with another constructor. In the first call to the constructor, The constructor with one argument is called, and i will be initialized with the value However, In the second call to the constructor, The constructor with the 2 arguments is called, and i will be initialized with the value There is no copy constructor in java.
In this example, we are going to copy the values of one object into another using java constructor. Here, the data type of the variables a and b, i. The output of the program is 0 because the variable i is initialized to 0 internally. As we know that a default constructor is invoked implicitly if there is no constructor in the class, the variable i is initialized to 0 since there is no constructor in the class.
There is a compiler error in the program because there is a call to the default constructor in the main method which is not present in the class. However, there is only one parameterized constructor in the class Test. Therefore, no default constructor is invoked by the constructor implicitly. The static variable is used to refer to the common property of all objects that is not unique for each object , e. Static variable gets memory only once in the class area at the time of class loading. Using a static variable makes your program more memory efficient it saves memory.
Static variable belongs to the class rather than the object. Because the object is not required to call the static method. If we make the main method non-static, JVM will have to create its object first and then call main method which will lead to the extra memory allocation. No, we can't override static methods. Static block is used to initialize the static data member. It is executed before the main method, at the time of classloading.
Ans Yes, one of the ways to execute the program without the main method is using static block. As we know that the static context method, block, or variable belongs to the class, not the object. Since Constructors are invoked only when the object is created, there is no sense to make the constructors static. However, if you try to do so, the compiler will show the compiler error.
In Java, if we make the abstract methods static, It will become the part of the class, and we can directly call it which is unnecessary. Calling an undefined method is completely useless therefore it is not allowed.
Yes, we can declare static variables and methods in an abstract method. As we know that there is no requirement to make the object to access the static context, therefore, we can access the static context declared inside the abstract class by using the name of the abstract class.
OOPS Interview Questions and Answers
OOP Object-oriented Programming is a programming paradigm that contains objects and fields to hold the data and methods to implement business logic. Each and every object can interact with each other based on their access level modifiers. The object-oriented paradigm is based on the classes and objects where objects are the instances of the classes and can be created in different ways. The main features of Object-oriented Programming techniques are Abstraction, Encapsulation, Inheritance, and Polymorphism. Most of the dynamic programming languages are based on OOPs principles. It is true that every interview is different as per the different job profiles but still to clear the interview you need to have a good and clear knowledge of OOP. Here, we have prepared the important OOP Interview Questions and Answers which will help you get success in your interview.
There is the list of core Java interview questions. If there is any core Java interview question that has been asked to you, kindly post it in the ask question section. The answers to the Core Java interview questions are short and to the point. The core Java interview questions are categorized in Basics of Java interview questions, OOPs interview questions, String Handling interview questions, Multithreading interview questions, collection interview questions, JDBC interview questions, etc. Java is the high-level, object-oriented , robust, secure programming language, platform-independent, high performance, Multithreaded, and portable programming language. It was developed by James Gosling in June
OOP Interview Questions
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.
Welcome to OOPS interview questions and answers.
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