I have got shared many posts most Java interview query inward the past times but nothing, especially for back upwardly engineer perspective. Since at that spot are a lot of L1 as well as L2 back upwardly task exists inward BFSI (Banking, Finance, as well as Insurance Industry) as well as they are also for the longer term, I decided to write this post. When you lot move for a back upwardly engineer role, especially for Java application live on it to heart as well as person Java or Java EE application, Interviewer expects you lot know basics of Java as well as tin start/stop the application, come across log files, warning developers, as well as other aspects of the back upwardly e.g. opening conference pair to solve production issues, communicating to stakeholders, as well as involving correct peoples. In this article, I volition percentage questions to assist with technical aspects e.g. the essential skills you lot demand to clear a back upwardly engineer interview.
Even though you lot volition live on interviewed to back upwardly Java application, it's expected from you lot to know SQL, UNIX, XML as well as other key technologies which you lot volition exercise inward your day-to-day job. In this post, you lot volition notice questions which are asked to banking concern represent whether a candidate has required skills to back upwardly Java application or not.
39 Interview Questions for Java JEE Support Engineers
Here is my collection of some of the best interview questions for Java as well as JEE back upwardly professionals. If you lot are working inward production services or supporting Java application, these interview query volition assist you lot to create good on your interview. If you lot moving from evolution to back upwardly role so also these questions volition give you lot a proficient thought most what is expected from a Java JEE back upwardly engineers.
1) How create you lot banking concern represent your Java procedure is running on Linux? (
example)
You tin banking concern represent past times using "ps" ascendancy as well as "grep" ascendancy e.g.
ps -ef | grep "myprocess". The keyword which you lot exercise with grep for search tin live on anything unique to your process, something which appears inward its ascendancy draw e.g. get upwardly of the shape which implements the primary method. You tin also create
"ps -ef | grep java" to listing all Java process.
2) How create you lot banking concern represent how much retention as well as CPU your Java procedure is consuming? First, you lot demand to notice the PID of your process, which you lot tin notice past times using the "ps" ascendancy equally shown inward the previous question. Once you lot notice the PID you lot tin exercise the
"top" ascendancy to notice the CPU as well as retention usage. Alternatively, you lot tin also exercise the
prstat ascendancy equally shown
here.
3) What does -Xmx as well as -Xms parameters mean? These are parameters to specify heap size inward Java. The -Xms defines the size of the heap when JVM starts upwardly as well as -Xmx is used to specify the maximum heap size for Java application i.e. your heap cannot grow beyond that as well as JVM volition croak past times throwing OutOfMemoryError if your heap doesn't have got plenty infinite to create novel objects. See
here to acquire to a greater extent than most heap retention inward Java.
4) What is the departure betwixt JVM as well as JRE? The JRE stands for Java Runtime Environment as well as JVM stands for Java Virtual Machine. You install JRE to run Java application e.g. Applet or Core Java application or Web server similar Tomcat. The JVM is business office of JRE. See
here to acquire to a greater extent than differences betwixt JVM as well as JRE.
5) What is the departure betwixt JVM as well as JIT? (
answer)
The JVM stands for Java Virtual machine spell JIT stands for Just inward fourth dimension Compiler. The JIT is business office of JVM as well as used to convert the Java bytecode into native machine code which runs faster. There is some threshold gear upwardly if a code runs to a greater extent than than the threshold it becomes the candidate of only inward fourth dimension compilation past times JIT.
6) How create you lot accept the heap dump of a Java process? There are many ways to accept the heap dump of a Java procedure e.g. Tomcat, but most mutual is past times using tools available inward JDK e.g. jVisualVM, jCmd, as well as jmap. Here is the ascendancy you lot tin exercise to accept the heap dump of Java process:
$ jmap -dump:live, file=/location/of/heap_dump.hprof PID
The heap dump volition comprise all alive objects as well as they are stored inward
heap_dump.hprof file. Remember, you lot also demand PID of Java procedure which you lot tin notice past times using "ps" as well as "grep" ascendancy equally discussed inward the source question. You tin come across
Java Performance Companion past times Charlie Hunt to acquire to a greater extent than most taking as well as analyzing heap dump inward Java to notice retention leak as well as other retention related errors.
Taking thread dump is easier than taking heap dump because you lot don't demand to call back tool. In Linux, you lot tin only exercise the kill ascendancy to accept the thread dump e.g.
$ kill -3 PID
volition impress the thread dump inward the log file or where System.out is redirected. Similarly, inward Windows, you lot tin exercise Ctrl + Break from the ascendancy prompt. Alternatively, you lot tin also exercise jConsole as well as VisualVM to accept the thread dump of Java application inward both Windows as well as Linux. You tin also read
Java Performance The Definitive Guide By Scott Oaks to acquire to a greater extent than most thread dump as well as heap dump.
8) What is OutOfMemoryError inward Java? How create you lot bargain with that? The Java virtual machine throws java.lang.OutOfMemoryError when at that spot is non plenty retention to run the application e.g. no to a greater extent than retention to create novel objects, no to a greater extent than retention to create novel threads etc. The most mutual OutOfMemoryError is the
java.lang.OutOfMemoryError: coffee heap space, which comes when at that spot is no to a greater extent than retention left to create a novel object.
9) What is the departure betwixt 32-bit as well as 64-bit JVM? (
answer)
The primary differences betwixt 32-bit as well as 64-bit JVM are that afterward is designed for 64-bit operating arrangement e.g. Windows 8 or afterward versions of Linux. From Java developer's perspective, the primary departure betwixt them comes from heap size. Influenza A virus subtype H5N1 64-bit JVM virtually has unlimited heap memory equally compared to 4GB of the theoretical bound of 32-bit JVM. If your plan needs to a greater extent than memory, meliorate run it on 64-bit JVM with large heap space. See hither to acquire to a greater extent than most 32-bit as well as 64-bit JVM.
13) What is Garbage Collector? (
answer)
The garbage collector is a element of Java virtual machine which is responsible for reclaiming retention from dead objects. It's i of the key components as well as allows an application developer to focus on application evolution rather than doing retention management. Some of the pop garbage collectors are a Concurrent Mark-Sweep garbage collector as well as G1 garbage collector inward recent times.
14) How create you lot analyze a heap dump? There are many tools to analyze heap dump inward Java e.g. you lot tin exercise the
jhat tool which comes along with JDK. You tin also exercise Eclipse Memory Analyzer to analyze heap dump to notice out whatever retention leak inward Java spell dealing with OutOfMemoryError inward Java. See
Java Performance The Definitive Guide By Scott Oaks to acquire to a greater extent than about analyzing Java Heap dump.
15) What is the departure betwixt Web Server as well as Application Server? (
answer)
The primary departure betwixt Web as well as Application Server comes from the fact that you lot cannot run EJB on the Web server similar Tomcat or Jetty. The application server similar WebLogic as well as WebSphere provides the runtime surroundings for EJB as well as other advanced services required past times Java EE or J2EE specification.
16) What is the departure betwixt Apache httpd as well as Tomcat? Though both httpd as well as Tomcat are products of Apache software foundation, the httpd is to a greater extent than pop as well as used across the spider web as well as non only inward Java world. The httpd is a spider web server which tin serve static HTML files as well as dynamic content using PHP, Perl or Python, spell Tomcat is a Servlet container which provides the runtime surroundings for
Servlet as well as
JSP. You tin also exercise both Apache httpd as well as Tomcat together inward Java world.
17) Can you lot exercise Apache as well as Tomcat together? Yes, you lot tin exercise Apache as well as Tomcat together. There are many Java spider web application which is fronted past times Apache spider web server to deliver static resources e.g. HTML files, images, configuration files etc. You tin so configure Apache to forwards the asking to
Tomcat.
18) How create you lot start as well as halt Tomcat inward Linux? When you lot install Tomcat inward Linux past times unzipping the downloaded package, you lot tin come across that at that spot is a
startup.sh as well as
shutdown.sh file inward the
tomcat/bin directory. These scripts are used to start as well as halt Tomcat inward Linux. These scripts internally telephone phone
Catalina.sh, the primary script to start
Tomcat engine.
19) How create you lot start as well as halt Apache inward Linux? The Apache server runs equally httpd daemon inward Linux as well as you lot tin either exercise
kill command after finding the PID of httpd procedure equally shown hither or you lot tin exercise the
apachectl script equally shown below to start as well as halt Apache spider web server inward Linux
Starting Apache spider web server inward Linux
$ apachectl start Stopping Apache
web server inward Linux
$ apachectl stop Restarting Apache spider web server inward Linux
$ apachectl restart
or:
/sbin/service httpd restart
You mightiness demand root access to create if
Apache spider web server is non running on your application account.
20) What is JDBC? The JDBC stands for Java Database connectivity as well as it provides API to connect a database from Java programs. Different Java vendors e.g.
MySQL,
Oracle,
Microsoft SQL Server, PostgreSQL they implement the API as well as provides their driver implementation to allow Java to connect to their database. Since almost every venture application has a database,
JDBC is real of import for whatever existent globe projects.
21) What is the departure betwixt JDBC as well as JNDI? As I said inward the previous answer, the JDBC stands for Java Database Connectivity as well as provides APIs as well as guidelines to connect a database from Java, spell JNDI stands for Java Naming as well as Directory Interface as well as provides a logical construction for retrieving resources e.g. database, messaging queues, venture Java beans without knowing their physical house e.g. host or port. You tin register a resources with JNDI as well as so residuum of your application element tin access them using JNDI name. The database connexion puddle is the most mutual resources accessed via JNDI inward
web servers similar Tomcat or WebLogic.
22) What is database connexion pool? (
answer)
As it get upwardly suggests, it only a puddle of database connections. Since creating a novel database connexion inward real-time is an expensive procedure as well as tin potentially deadening downwards the response time, many application maintains a puddle of active database connection. When a
request comes inward they retrieve a connexion from the pool, acquire the information from the database as well as so render the connexion dorsum to puddle so that it tin live on reused. This way, response fourth dimension is improved inward most of the Java spider web application. See
here to setup a database connexion puddle inward Tomcat using Spring framework.
23) Your Java application is connected to a Database via a connexion pool. Suddenly your database goes down? Is that an number with your Java application? Do you lot demand to restart your Java application? hint: Since your Java application is using a connexion pool, it has active connections to database which volition acquire disconnected i time DB goes down. If you lot attempt to execute a query, you lot volition have Socket errors.
24) How create you lot shipping spider web service asking from Linux? (
answer)
There are some commands available inward Linux e.g. curl as well as wget which allows you lot to shipping HTTP commands, which you lot tin exercise to telephone phone as well as essay your spider web services from Linux. Particular, Curl is used extensively to essay
RESTful Web Services because it tin shipping POST request, GET request, asking with headers as well as also authenticate using both basic as well as digest authentication.
If you lot are working with REST API, I advise
learning curl, it's real convenient to banking concern represent if your API is working properly using curl from the ascendancy line. You tin fifty-fifty write a script to automate those stuff.
25) What is the departure betwixt HTTP as well as HTTPS? (
answer)
This is i of the mutual as well as like shooting fish in a barrel questions. Of course, you lot know the departure betwixt HTTP as well as HTTPS right? well, HTTP is insecure but HTTPS is secure, the extra "s" is for security, which agency it non exclusively encode as well as encrypt the message earlier sending but also verify the identity of the server past times using SSL certificates provided past times global certificate government e.g. GoDaddy, Thawte, VeriSign, Digicert, GeoTrust, as well as Comodo. See
here to acquire to a greater extent than how SSL as well as Certifications run inward Java spider web application.
26) What is the departure betwixt the GET as well as POST method? (
answer)
Another uncomplicated but ofttimes asked query on Java back upwardly interviews. The primary departure betwixt the GET as well as POST is that GET is both
idempotent and rubber but POST is not. You tin burn GET asking multiple fourth dimension as well as it volition give the same number but multiple POST submission should ever live on avoided. GET is also used to read information from server as well as
POST is used to shipping information to the server.
27) What is the departure betwixt Servlet as well as JSP? (
answer)
This is some other interesting Java JEE back upwardly Interview Question. Even though both Servlet as well as JSP is used to create dynamic HTML the key departure betwixt them is their purpose. Servlet is meant for Java developers as well as you lot write to a greater extent than Java than HTML as well as that's why it serves equally Controller inward many pop MVC framework e.g.
DispatcherServlet inward Spring MVC.
On the other hand, JSP is designed for HTML developers as well as it's to a greater extent than HTML than Java as well as that's why it is used equally "view" inward MVC frameworks similar Spring as well as Struts. See the link inward the reply for to a greater extent than detailed comparison.
28) What is the departure betwixt Struts as well as Spring MVC? This is i time again a pop as well as ofttimes asked query on Java JEE Interviews. Even though both are pop spider web MVC framework for Java applications, the key departure is that Spring brings dependency injection source as well as Struts brings it afterward using
Struts 2.0.
Spring is also a suite of libraries e.g. you lot acquire Spring Security to implement safety inward your application, so at that spot is Spring Boot, Spring Data, Spring Cloud as well as many to a greater extent than useful libraries nether
Spring umbrella.
answer)
There are many differences betwixt JDBC as well as Hibernate but the most of import i is that JDBC provides an API to connect to the database as well as execute the query but Hibernate is an ORM (Object Relational modeling) framework, which agency it allows you lot to run with objects spell it takes aid of saving as well as retrieving object from database.
In short, inward JDBC you lot demand to write
SQL queries to acquire as well as shop information from database but inward Hibernate you lot only bargain with objects, Hibernate takes aid of issuing SQL queries to the database.
30) What is the departure betwixt Stack retention as well as heap? Which i is faster? (
answer)
These are only 2 dissimilar retention areas used to shop dissimilar kinds of variables. The stack is local to every thread spell heap retention is shared alongside all threads. Since Stack is closer to thread as well as unremarkably implemented using CPU registers they are faster than
heap memory. The stack is used to shop local variables equally good method telephone phone frames spell heap is used to shop objects as well as shape metadata. See the detailed reply for to a greater extent than points.
31) What is the departure betwixt TCP/IP as well as UDP protocol? (
answer)
There are several differences betwixt TCP as well as UDP protocol but the most of import of them is that TCP provides a guarantee of message delivery spell UDP doesn't give whatever guarantee. Because of this guarantee
TCP sends to a greater extent than messages than UDP as well as thus eat to a greater extent than bandwidth as well as slower than UDP. TCP is also connexion oriented protocol spell UDP is connectionless. See the detailed reply for to a greater extent than points.
32) Your Java application is connecting to some other Java application (server) running on the remote host as well as listening on port 17865. Now, you lot don't have got access to that remote host to move as well as come across if the procedure is running. How create notice if the server is upwardly as well as running? hint: you tin exercise the
telnet command
33) You are supporting a Java spider web application which connects to many heart as well as person Java procedure as well as gets information from them to the distribution to clients? One customer complains that the asking for information is taking also long as well as it's almost similar hung? How create you lot troubleshoot this problem? hint: banking concern represent the log, banking concern represent database, banking concern represent the file system
34) The Java application you lot back upwardly connects to a database via a DNS, which automatically switches to the secondary database server when the primary goes down. You notice that inward the trial of a failover, your Java application is non connecting to secondary DB server? How create you lot troubleshoot this problem? hint: banking concern represent which version your Java application is running. Some
JRE caches the DNS e.g. JRE 1.6
answer)
The deadlock is a status which tin occur betwixt 2 or multiple threads. In this case, each of the thread waits for each other as well as cannot progress. In Java, this unremarkably happens when thread 1 holds the lock required past times thread 2 as well as thread 2 holds the lock required past times thread 1. If your Java plan is hung so it could live on a
deadlock. You tin accept a thread dump as well as notice out if whatever thread is waiting for the lock concord past times other as well as vice-versa. You tin also exercise jConsole tool to notice deadlock.
36) What is the race condition? (
answer)
The race status is some other multithreading as well as concurrency põrnikas which happens due to racing betwixt 2 threads, for example, if i thread is updating a variable as well as minute thread tries to read the value earlier it finished. You tin avoid race weather condition past times properly synchronizing your code.
37) What is the departure betwixt PATH as well as CLASSPATH? (
answer)
Both are key surroundings variable used past times Java platform, but the key departure betwixt them is that PATH points to the JDK binaries or native libraries e.g. java.exe, spell CLASSPATH points to Java binaries e.g. JAR files, which contains bytecode. PATH is also arrangement marker concept independent of Java but
CLASSPATH is purely Java concept as well as used past times JVM to charge classes required past times Java application you lot are running.
38) How create you lot notice the Java version used past times your application? (
answer)
You tin run the coffee -version ascendancy inward the ascendancy prompt to notice out the version of Java used past times your application. If you lot have got multiple JDK or JRE installed so brand certain you lot exercise the i which is used past times your application.
39) What is JAVA_HOME surroundings variable? (
answer)
The JAVA_HOME is zero but a user defined surroundings variable which points to the installation directory of JDK. For example, if you lot have got installed JDK inward /opt/jdk_1.6_20 inward Linux so the
JAVA_HOME variable volition betoken to this directory. Same goes for Windows or whatever other operating system.
That's all most
39 essential questions fro Java JEE Support Engineer. It's only a pocket-size gear upwardly of questions you lot tin hold off inward whatever service based companionship or investment banks but does call back to create key skills required for back upwardly engineers e.g. UNIX, SQL, Java, as well as others. In the adjacent business office of this article, I volition percentage some of the ofttimes asked questions from Java Support Engineer on SQL, UNIX, as well as other supporting technologies.
Other
topic based Java Interview questions for to a greater extent than practice
- 21 Java Inheritance Interview Questions as well as Answers (list)
- 15 Data Structure as well as Algorithm Questions from Java Interviews (read here)
- Top 10 Spring Framework Interview Questions with Answers (see here)
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- 10 JDBC Interview Questions for Java Programmers (questions)
- 15 Java NIO as well as Networking Interview Questions with Answers (see here)
- 20 Java Design Pattern Questions asked on Interviews (see here)
- 10 Struts Interview Questions for Java developers (list)
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- 10 ofttimes asked Servlet Interview Questions with Answers (see here)
- 15 Java Enum based interview questions with answers (read)
- 10 Oracle Interview Questions for Java developers (see here)
- Top 10 JSP Questions from J2EE Interviews (read here)
- 12 Good RESTful Web Services Questions from Interviews (read here)
- Top 10 EJB Interview Questions as well as Answers (see here)
- Top 10 JMS as well as MQ Series Interview Questions as well as Answers (list)
- 10 Hibernate Interview Questions for Java EE developers (see here)
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- Top 10 XSLT Interview Questions with Answers (read more)
- Top 10 Trick Java Interview Questions as well as Answers (see here)
- Top xl Core Java Phone Interview Questions with answers (list)
This list of Java interview questions for Java, JEE, as well as J2EE back upwardly engineers should live on plenty to create for whatever Java interview. You tin crevice both fresher as well as sense marker interview past times preparing these Java interview questions, at to the lowest degree source few rounds. If you lot human face upwardly whatever other interesting query which is non inward this list, so delight permit me know via comments as well as I'll add together it.
Further Learning Java Web Fundamentals By Kevin Jones Spring Framework 5: Beginner to Guru JSP, Servlets as well as JDBC for Beginners: Build a Database App
Here are my listing of questions which is worth preparing if yous are going for total coffee interview for senior position, these questions are to a greater extent than oftentimes than non based upon Garbage collection , Concurrency, Collections, design, Coding in addition to testing.
