Java Interview Questions And Answers For Experienced Programmers:
Java has become indispensable for developing application and web software. The programming language can be studied in two parts – basics and advanced. The fresh aspirants study the following – control structures, arrays and methods, OOP principles, Strings and Characters, Graphics, Applets, etc.,
The more experienced candidates can study the following advanced concepts after revising the basics thoroughly – Exception Handling, Multithreading, Multimedia, Files and Streams, JDBC, Servlets, RMI, Beans, Collections, and Networking.
The interviews for java professionals and experienced programmers are used to gauge deeper comprehension and advanced application skills. The questions and answers does not cover the basics, but more complex topics are discussed as specified below –
Define a data structure with examples?
A data structure is a storage and organization method for related data. In Java, The arrays are called static data structures as their size in terms of memory allocated cannot be changed. Lists, queues, stacks, and trees are dynamic data structures which grow or shrink in size during program execution.
Give the names of 4 legacy data structures from java utility package?
Enumeration, Dictionary, Vector, and Hash table are legacy data structures that have been replaced by the new Collections Framework.
What are the names of 6 different sorting techniques?
The following sorting techniques are used to arrange data based on storage requirements and efficiency – Bubble Sort, Quick Sort, Selection Sort, Merge Sort, Insertion Sort, and Heapsort.
What are ObjectInputStream and ObjectOutputStream Classes?
They are JVM-independent high-level streams which provide the methods for serializing and De-serializing an object.
What do you mean by serializing and deserializing an object?
The Java mechanism for representing an object as a sequence of bytes including object data and metadata. The serialized data can be written to a file and extracted back again to recreate the object, which is called deserializing.
What are Collections in Java?
Java Collections framework is a group of pre-packaged data structures and algorithms that can be used by programmers and developers. Code can be reused to quickly write efficient programs with minimal memory allocation requirements.
Name three interfaces that are a part of Java Collections?
The Collection, Iterator, and Enumeration are three interfaces found in Collections.
What are five abstract data types that use (key, value) pairs?
Associative array, hash table, symbol table, dictionary, and map are five abstract data types that use the (key, value) pair.
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What are JVM, JRE, and JDK ?
JVM is a part of JRE which itself is a subset of JDK. JVM or java virtual machine is the layer which runs java byte codes by interacting with the underneath OS like Mac OS, Linux, Windows, etc., JRE (Java Runtime Environment) includes JVM, libraries, components that run applications and applets, Java Plug-in and Java Web Start. JDK (Java Development Kit) contains JRE and development tools like compilers, debuggers, archiver, document generator, etc.,
Name four classes used for writing networking applications in java?
Four classes that are used to write networking applications are DatagramPacket, DatagramSocket, BindException, and ConnectException classes.
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What is a java platform and how many platforms are there?
Java platform refers to the particular environment in which java programs are executed.There are 4 different platforms called as SE, EE, ME, and FX i.e. Java Standard Edition, Java Enterprise Edition, Java Micro Edition and Java FX platforms. They are used to develop medium-scale, large-scale, mobile, and internet java programs respectively.
What are integral operands and bitwise operators? What type of applications make use of them?
Integral operands have the types – byte, char, short, int, and long. The bit wise operators like AND, OR, left shift, right shift, complement, etc., are used to manipulate the bits of these operands. These java features are used in writing applications for operating systems, testing equipment, and in networking by directly communicating with the hardware.
What is a server?
Computers that are connected interact using a client-server model. The computer that makes a request for service or data is called a client and the computer or set of computers that respond to the client’s request by transmitting data are called servers.
What is a java servlet?
Servlets in java are programs that are stored and executed in the server environment.
How are servlets implemented in java?
Java servlets can be written using the javax.servlet and javax.servlet.http packages. All java classes for servlet programming must implement the javax.servlet.Servlet interface.
What is Java Servlet API?
Java Servlet API is a predefined and encapsulated set of classes and interfaces that are used for writing server-side programs. The API is provided as a standard extension to the platform and the top-level package uses the “javax” name instead of the familiar name “java”.
Can you write java servlets using Java SE platform?
No. We need the Java Servlet API to compile the servlets and it is available only with the java EE (Enterprise Edition) platform.
What are the names of five popular java server side technologies?
Java server side technologies include JSP (Java Server Pages), JSF (Java Server Faces), Struts, Spring, and Hibernate.
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What are Java Beans?
Java Beans are classes which can encapsulate multiple objects into a single object called a bean or more precisely a JavaBean. They have zero-argument constructors and can be serialized. They are used in rapid application development by writing reusable software components.
How do you interact with databases using java?
Java uses software components called JDBC Drivers to interact with databases.
What is the full form and definition of JDBC API?
JDBC stands for Java Database Connectivity Application Programming Interface. JDBC is the industry-standard, database-independent set of protocols, procedures, and tools that are used for writing java programs to access various databases available in the market.
How do objects running on different Java Virtual Machines (JVM) communicate?
An object running on one JVM can call a method of a different object running on another JVM using the RMI i.e. Remote Method Invocation model.