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Java Interview Questions And Answers Pdf Yes, We can execute any code, even before the main method. We are using a static block. In this guide we will discuss about different types of questions that can be used in a Java interview, in order for the employer to test your skills in Java and. 5) Difference between method overloading and method overriding in java? . .. 9. 6) Difference . Core java Interview questions on Coding Standards.
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. A sub-class is a class which inherits from another class called super class. Sub-class can access all public and protected methods and fields of its super class. What are the various access specifiers for Java classes?
They can be stored in compressed files called JAR files. The Packages in this general purpose language have following features :- 1. Package provides a unique namespace for the types it contains.
Answer- When a method of the same name and signature is included in both super and subclasses then the method in the subclass is said to override the method in superclass. Question 8-What do you mean by Multithreaded programming in Java? Answer- A multithreaded program contains two or more parts that can run concurrently.
Each of these part is known as a thread which is the smallest unit of dispatchable code. Answer- It is a strongly typed language because: Every variable and expression has a strongly defined type.
All assignments are checked for type compatibility.
Question 4- Draw a diagrammatic representation of Java? Answer- Architecture can be represented as: Question 5- What do you mean by Java Applet? Answer- An applet is a special kind of Java program that is designed to be transmitted over the internet and automatically executed by a Java compatible web browser. They are downloaded on demand without interacting with user. The following figure explains loading and start-up of an applet.
Question 6- How will you define packages in java? Answer- A package is a mechanism for organising the classes. They can be stored in compressed files called JAR files. The Packages in this general purpose language have following features: Package provides a unique namespace for the types it contains.
Answer- When a method of the same name and signature is included in both super and subclasses then the method in the subclass is said to override the method in superclass.
Question 8-What do you mean by Multithreaded programming in Java? Answer- A multithreaded program contains two or more parts that can run concurrently. Each of these part is known as a thread which is the smallest unit of dispatchable code.
Another key difference in the use of abstract classes and interfaces is that a class which implements an interface must implement all the methods of the interface while a class which inherits from an abstract class doesn't require implementation of all the methods of its super class.
A class can implement multiple interfaces but it can extend only one abstract class.
What are the performance implications of Interfaces over abstract classes? Ans: Interfaces are slower in performance as compared to abstract classes as extra indirections are required for interfaces. Another key factor for developers to take into consideration is that any class can extend only one abstract class while a class can implement many interfaces. Use of interfaces also puts an extra burden on the developers as any time an interface is implemented in a class; developer is forced to implement each and every method of interface.
Does Importing a package imports its sub-packages as well in Java? Ans: In java, when a package is imported, its sub-packages aren't imported and developer needs to import them separately if required. For example, if a developer imports a package university. To load the classes from its sub-package say department , developer has to import it explicitly as follows: Import university. Can we declare the main method of our class as private?
Ans: In java, main method must be public static in order to run any application correctly. If main method is declared as private, developer won't get any compilation error however, it will not get executed and will give a runtime error.
How can we pass argument to a function by reference instead of pass by value? Ans: In java, we can pass argument to a function only by value and not by reference. How an object is serialized in java?
Ans: In java, to convert an object into byte stream by serialization, an interface with the name Serializable is implemented by the class. All objects of a class implementing serializable interface get serialized and their state is saved in byte stream. When we should use serialization? Ans: Serialization is used when data needs to be transmitted over the network.
Using serialization, object's state is saved and converted into byte stream. The byte stream is transferred over the network and the object is re-created at destination. Ans: Try block needs to be followed by either Catch block or Finally block or both. Any exception thrown from try block needs to be either caught in the catch block or else any specific tasks to be performed before code abortion are put in the Finally block.
Is there any way to skip Finally block of exception even if some exception occurs in the exception block? Ans: If an exception is raised in Try block, control passes to catch block if it exists otherwise to finally block.
Finally block is always executed when an exception occurs and the only way to avoid execution of any statements in Finally block is by aborting the code forcibly by writing following line of code at the end of try block: System.
When the constructor of a class is invoked? Ans: The constructor of a class is invoked every time an object is created with new keyword.
For example, in the following class two objects are created using new keyword and hence, constructor is invoked two times. Can a class have multiple constructors? Ans: Yes, a class can have multiple constructors with different parameters. Which constructor gets used for object creation depends on the arguments passed while creating the objects.
Can we override static methods of a class? Ans: We cannot override static methods.
Static methods belong to a class and not to individual objects and are resolved at the time of compilation not at runtime. Even if we try to override static method,we will not get an complitaion error,nor the impact of overriding when running the code. In the below example, what will be the output? Is String a data type in java? Ans: String is not a primitive data type in java. When a string is created in java, it's actually an object of Java.
String class that gets created. After creation of this string object, all built-in methods of String class can be used on the string object.
In the below example, how many String Objects are created? String class are created. Why Strings in Java are called as Immutable? Ans: In java, string objects are called immutable as once value has been assigned to a string, it can't be changed and if changed, a new object is created. In below example, reference str refers to a string object having value "Value one". What's the difference between an array and Vector? Ans: An array groups data of same primitive type and is static in nature while vectors are dynamic in nature and can hold data of different data types.
What is multi-threading? Ans: Multi threading is a programming concept to run multiple tasks in a concurrent manner within a single program. Threads share same process stack and running in parallel. It helps in performance improvement of any program. Why Runnable Interface is used in Java?
Ans: Runnable interface is used in java for implementing multi threaded applications. Runnable interface is implemented by a class to support multi threading. What are the two ways of implementing multi-threading in Java? Ans: Multi threaded applications can be developed in Java by using any of the following two methodologies: 1.
By using Java. Runnable Interface. Classes implement this interface to enable multi threading.