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Top 10 Java Interview Questions with Answer

How Java achieves platform independence?
When we say Java is platform independent which means Java programs are not dependent on any platform, architecture or operating system like windows or Linux. Java achieve this by using Java virtual machine, when Java programs are compiled they are converted to .class file which is collection of byte code and directly understandable  by JVM. So the same Java program can run on any operating system only JVM can differ according to OS but all JVM can understand converted byte code that's how Java achieve platform independence. 

Life Cycle of JVM :

When a Java application starts, a runtime instance is born. When the application completes, the instance dies. If you start three Java applications at the same time, on the same computer, using the same concrete implementation, you'll get three Java virtual machine instances. Each Java application runs inside its own Java virtual machine.

For Example :

If we have a Node manager which contains 3 Managed server having instance of JVM, then there will be 3 instance of JVM running on managed server, all of them will be pointing to the Node manager.

The source code is first written in plain text files ending with the .java extension. Those source files are then compiled into .class files by the javac compiler. A .class file does not contain code that is native to your processor; it instead contains bytecodes — the machine language of the Java Virtual Machine (Java VM). The java launcher tool then runs your application with an instance of the Java Virtual Machine.

java interview questions

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More New Features Coming for Java 9

Java 8 arrived earlier this year to much fanfare, including high marks for lambda expressions and JavaScript on the JVM via Nashorn.

Expected in early 2016, Java Development Kit 9, based on the Java Standard Edition 9 specification, is expected to include
i) performance tweaks,
ii) new capabilities,
iii) most notably, modularity.

While some proposed features could miss the final cut or be postponed to a later release, there's already a lot to like about Java's proposed future.

Here are some of the major features...
  1.     A light-weight JSON API
  2.     A HTTP 2 Client
  3.     Process API Improvements  — to improve the API for controlling and managing OS processes.
  4.     Improved contended locking — for increasing performance between threads.
  5.     Segmented Code Cache — to improved execution time for complicated benchmarks.
  6.     Smart Java Compilation (Part 2) — Makes the sjavac tool available in the default JDK.
  7.     Modular Source Code — organizes JDK source code into modules

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Which is Secured? Java Or Dot Net?

Software industry by its nature is always in flux thus no particular technical skill will grant you job security. It is always advisable to not choose the technology just because today it is paying you more. Rather than Logical thinking and Hard work, no programming language provide you secured job and good salary.

Intangible skills are better at helping secure a job. Be a good people person, analyst, learner and know how to adapt to changing times. Also depending on where you are, different skill sets could be more or less valuable relative to the world-wide trends. Around here, Java and COBOL are still both considered good skills to have on one's profile/resume.
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Salary of Freshers in Java

In many cases, Salary for a fresher candidates decides which is her/his first company. Salary depends on the below criteria

  1. Your College / University
  2. % of Marks you Scored
  3. Company
  4. Work Location

Service Industry MNCs in India like TCS, HCL, Infosys may pay you from 3.5 to 4.5 lakh per annum if you scored a good marks (70% and above) and other MNCs might pay you even more up to 6 to 8 Lakh. This average salary varies based on the above four criteria. Salary vary if you are in same company, same level, same skill set and experience but in different location. For example, salary in Bangalore must be different from Salary in Hyderabad.

Many product companies are fiercely competing with rivals and start ups to attract the best coding brains in the industry. "A great developer is well worth his/her weight in gold. The theory subscribed to here is that a great developer is 5x-10x better than an average developer and that's the basic law of software engineering talent," said Ravi Gururaj, chairman of the Nasscom Product Council.

HackerEarth finds that Indian startups Druva, Flipkart, Practo, Freshdesk, global start ups PassportParking and big names such as VMware, Intuit and Intel offer fresher and mid-level salaries in the Rs 7 lakh to Rs 12 lakh range for those with high-level programming skills.

As per the PayScale website, here is the average salary for an entry level Software Engineers.

Courtesy: PayScale, TimeofIndia
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Best Java Books: Head First Java by Kathy Sierra and Bert Bates

Head First Java
Best Java Book
Head First Java by Kathy Sierra and Bert Bates is a pretty well constructed book for beginners. It compresses the time it takes to learn and retain--complex information. Its unique approach not only shows you what you need to know about Java syntax, it teaches you to think like a Java programmer. If you want to be bored, buy some other book. But if you want to understand Java, this book's for you.

You'll learn everything from the fundamentals to advanced topics, including threads, network sockets, and distributed programming with RMI. And the new. second edition focuses on Java 5.0, the latest version of the Java language and development platform. Because Java 5.0 is a major update to the platform, with deep, code-level changes, even more careful study and implementation is required. So learning the Head Firstway is more important than ever.

Click here to get the Book from Flipkart
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