Difference Betwixt Url, Uri Too Urn - Interview Question

All 3 URI, URL, in addition to URN are used to position whatsoever resources or cite on the internet, but at that topographic point is a subtle departure betwixt them. URI is the superset of both URL in addition to URN. By the way, the master copy difference betwixt URL in addition to URI is protocol to retrieve the resource. URL ever include a network protocol e.g. HTTP, HTTPS, FTP etc to retrieve a resources from its location. While URI, inwards representative of URN only uniquely identifies the resources e.g. ISBN numbers which are a skillful representative of URN is used to position whatsoever mass uniquely. In this article, nosotros volition briefly run into what is URI, URL, in addition to URN in addition to hence run into the main departure betwixt URI, URL, in addition to URN.

What is URI

URI stands for Uniform Resource Identifier. URI is a text which is used to position whatsoever resources or cite on Internet. URI has ii specializations inwards the shape of URL (Uniform Resource Locator) in addition to URN (Uniform Resource Name) to position resources in addition to name. We generally run into examples of URL in addition to URN inwards the existent word. If y'all are working on JSP in addition to familiar alongside using tag library e.g. display tag in addition to JSTL gist tag library, hence y'all may think the move of URI to locate binary corresponding to a tag library.

What is URL

URL standards for Uniform resources locator in addition to it is a subset of URI or Uniform Resource Identifier. URL includes place every bit good every bit the protocol to retrieve the resources e.g. inwards /search?q=displaytag-examples-tutorial-jsp-struts, HTTP is a protocol which tin forcefulness out endure used to retrieve resources what-is-new-in-java-7-top-5-jdk-7.html available inwards place http://java67.blogspot.com directory. It's non necessary that URL ever include HTTP every bit protocol, it tin forcefulness out move whatsoever protocol e.g. ftp://, https:// or ldap://.

What is URN

URN stands for Uniform Resource Name. URN is likewise the subset of URI. One of the best examples of URN is ISBN number which is used to uniquely position a book. URN is completely unlike than URL every bit it doesn't include whatsoever protocol.

Difference betwixt URI, URL, in addition to URN

After knowing what is URI, URL, in addition to URN, it's slow to notice the departure betwixt them. The master copy departure betwixt URI in addition to URL is that every URL is a URI but non vice versa. Similarly, every URN is a URI, but the reverse is non true. Another departure betwixt URI in addition to URL is that URL includes the protocol, which is telephone substitution to retrieving information from whatsoever location. Here are few differences betwixt URI, URL in addition to URN inwards betoken format:

1) Every URL in addition to URN is URI because URI is the superset of both URL in addition to URN.

2) URL includes protocol e.g. http://, ftp:// along alongside place to position resources e.g. http://www.blogspot.com/abc.html.

3) URN are the unambiguous agency to position a resource. ISBN numbers are best examples of URN.

Here is a diagram which clearly reverberate the human relationship of URL, URI, in addition to URN on the internet:

That's all on the difference betwixt URI, URL, in addition to URN. It’s skillful to know how much departure they are though y'all generally postulate to bargain alongside URL.

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Difference Betwixt Set, Listing Together With Map Inwards Coffee - Interview Question

Set, List together with Map are 3 of import interfaces of Java collection framework together with Difference betwixt Set, List, together with Map inwards Java is ane of the close oft asked Java Collection interview question. Sometimes this enquiry is asked every bit When to usage List, Set together with Map inwards Java. Clearly, the interviewer is looking to know that whether you lot are familiar alongside fundamentals of Java collection framework or not. In gild to determine when to usage List, Set or Map, you lot demand to know what are these interfaces together with what functionality they provide. List inwards Java provides ordered together with indexed collection which may comprise duplicates. 

The Set interface provides an unordered collection of unique objects, i.e. Set doesn't allow duplicates, spell Map provides a information construction based on key-value duo together with hashing. 

All 3 List, Set, together with Map are interfaces inwards Java together with at that topographic point are many concrete implementations of them are available inwards Collection API. ArrayList together with LinkedList are ii close pop used List implementation spell LinkedHashSet, TreeSet, together with HashSet are oft used Set implementation. 

In this Java article, nosotros volition run into the difference betwixt Map, Set, together with List inwards Java together with larn when to usage List, Set or Map.

Set vs List vs Map inwards Java

As I said Set, List together with Map are interfaces, which defines essence contract e.g. a Set contract says that it tin non comprise duplicates. Based on our cognition of List, Set together with Map let's compare them on dissimilar metrics.

Duplicate Objects

The psyche departure betwixt List together with Set interface inwards Java is that List allows duplicates spell Set doesn't allow duplicates. All implementation of Set laurels this contract. 

While a Map holds ii objects per Entry e.g. a key together with a value together with It may comprise duplicate values simply keys are e'er unique. See here for to a greater extent than departure betwixt List together with Set information construction inwards Java. 

Order

Another key departure betwixt List together with Set is that List is an ordered collection, List's contract maintains insertion gild or element. Set is an unordered collection, you lot acquire no guarantee on which gild chemical component volition live on stored. 

Though around of the Set implementation e.g. LinkedHashSet maintains order. Also SortedSet together with SortedMap e.g. TreeSet together with TreeMap maintain a sorting order, imposed past times using Comparator or Comparable.

Hashtable doesn't allow nada key or values simply HashMap allows nada values together with ane nada key.  This is too the psyche departure betwixt these ii pop implementations of Map interface, aka HashMap vs Hashtable. 

Useful implementations
Most pop implementations of List interface inwards Java are ArrayList, LinkedList, together with Vector class. ArrayList is to a greater extent than full general purpose together with provides random access alongside index, spell LinkedList is to a greater extent than suitable for oft adding together with removing elements from List.

Vector is synchronized counterpart of ArrayList. On the other hand, close pop implementations of the Set interface are HashSet, LinkedHashSet, together with TreeSet. First ane is full general purpose Set which is backed past times HashMap, run into how HashSet plant internally inwards Java for to a greater extent than details.

It too doesn't render whatever ordering guarantee simply LinkedHashSet does render ordering along alongside uniqueness offered past times the Set interface.

Third implementation TreeSet is too an implementation of SortedSet interface, therefore it keeps elements inwards a sorted gild specified past times compare() or compareTo() method.

Now the final one, close pop implementation of Map interface is HashMap, LinkedHashMap, Hashtable, together with TreeMap.

First ane is the non-synchronized full general purpose Map implementation spell Hashtable is its synchronized counterpart, both doesn' render whatever ordering guarantee which comes from LinkedHashMap. Just similar TreeSet, TreeMap is too a sorted information construction together with keeps keys inwards sorted gild (see ArrayList provides faster access if you lot know index.

2) If you lot desire to shop elements together with desire them to maintain an order on which they are inserted into a collection so boot the bucket for List again, every bit List is an ordered collection together with maintain insertion order.

3) If you lot desire to practise a collection of unique elements together with don't desire whatever duplicate than choosing whatever Set implementation e.g. HashSet, LinkedHashSet or TreeSet. 

All Set implementation follow at that topographic point full general contract e.g. uniqueness simply too add together improver characteristic e.g. TreeSet is a SortedSet together with elements stored on TreeSet tin live on sorted past times using Comparator or Comparable inwards Java. LinkedHashSet also maintains insertion order.

4) If you lot shop information inwards shape of key together with value than Map is the agency to go. You tin direct from Hashtable, HashMap, TreeMap based upon your subsequent need. In gild to direct betwixt outset ii run into the difference betwixt HashSet together with HashMap inwards Java.

That's all on the difference betwixt Set, List, together with Map inwards Java. All 3 are the close cardinal interface of Java Collection framework together with whatever Java developer should know at that topographic point distinguish characteristic together with given a province of affairs should live on able to selection correct Collection shape to use.  You tin too farther see, When to usage Vector or ArrayList etc. Collection API is huge together with it's hard to know every bits together with slice simply at the same time, at that topographic point is no excuse for non knowing fundamentals similar the departure betwixt Set, List, together with Map inwards Java.

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Jdbc - How To Connect Mysql Database From Coffee Programme Amongst Example

When you lot start learning JDBC inwards Java, the showtime programme you lot desire to execute is connected to database from Java together with acquire roughly effect dorsum past times executing roughly SELECT queries. In this Java program, nosotros volition larn How to connect to MySQL database from Java program together with execute a query against it. I pick out MySQL database because it's costless together with tardily to install together with setup. If you lot are using Netbeans IDE thus you lot tin flame connect MySQL Server straight from Netbeans, Which agency inwards ane window you lot could live on writing Java code together with other you lot tin flame write SQL queries. Another wages of using MySQL database is that it provides type iv JDBC driver bundled inwards mysql-connector-java-5.1.17-bin.jar which is tardily to use. By the way, if you lot are using Oracle database thus you lot tin flame depository fiscal establishment jibe Java programme to connect Oracle database, to connect together with run SQL queries against Oracle DB.


This Java tutorial every bit good explains roughly of the mutual fault which comes spell working inwards JDBC code e.g. during connexion or reading results. In social club to connect to MySQL database you lot demand iii things database URL, username, together with password together with nosotros are using default user origin here, which is created during MySQL installation.

By the way, you lot tin flame every bit good use PreparedStatement for connexion because it’s ane of the JDBC best practice to purpose PreparedStatement for amend performance together with avoiding SQL Injection.

Java Program to Connect MySQL Database to Execute Query

Here is consummate Java programme to connect MySQL database running on localhost together with executing queries against that. This illustration connects to exam database of MySQL server, running on the local host at port 3306. At set down level, nosotros demand a JDBC connexion object to communicate amongst MySQL database, a Statement object to execute the query together with a ResultSet object to acquire effect from database. By the way you lot tin flame every bit good purpose Rowset object together with difference betwixt RowSet together with ResultSet is ane of the often asked JDBC Interview question.

One of the affair which I don’t similar most JDBC is lots of boiler plate code e.g. closing connection, contestation together with effect laid together with other resources inwards finally block. Once you lot motility ahead together with start using framework similar Spring, you lot tin flame purpose JdbcTemplate to avoid these boilerplate coding. It’s every bit good skillful to setup your tabular array together with information earlier writing Java program. We volition live on using next tabular array for query:

mysql> select * from stock; +---------+-------------------------+--------------------+ | RIC     | COMPANY                 | LISTED_ON_EXCHANGE | +---------+-------------------------+--------------------+ | 6758.T  | Sony                    | T                  | | GOOG.O  | Google Inc              | O                  | | GS.N    | Goldman Sachs Group Inc | northward                  | | INDIGO  | INDIGO Airlines         | NULL               | | INFY.BO | InfoSys                 | BO                 | | VOD.L   | Vodafone Group PLC      | L                  | +---------+-------------------------+--------------------+ 6 rows in set (0.00 sec)

And this is our Java programme to connect MySQL database together with you lot demand to add together mysql-connector-java-5.1.17-bin.jar into classpath, which contains JDBC type iv driver required to connect MySQL database. If you lot don’t include this JAR inwards your classpath, you lot volition acquire next fault java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

package test;  import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.logging.Level; import java.util.logging.Logger;  /**  *  * Java programme to connect to MySQL Server database running on localhost,  * using JDBC type 4 driver.  *  * @author http://java67.blogspot.com  */ public class MySQLTest{      public static void main(String args[]) {         String dbURL = "jdbc:mysql://localhost:3306/test";         String username ="root";         String password = "root";                 Connection dbCon = null;         Statement stmt = null;         ResultSet rs = null;                 String query ="select count(*) from stock";                 try {             //getting database connexion to MySQL server             dbCon = DriverManager.getConnection(dbURL, username, password);                         //getting PreparedStatment to execute query             stmt = dbCon.prepareStatement(query);                         //Resultset returned past times query             rs = stmt.executeQuery(query);                         while(rs.next()){              int count = rs.getInt(1);              System.out.println("count of stock : " + count);             }                     } catch (SQLException ex) {             Logger.getLogger(CollectionTest.class.getName()).log(Level.SEVERE, null, ex);         } finally{            //close connexion ,stmt together with resultset here         }             }       }  Output: count of stock : 6

ResultSet is used to recollect query effect If you lot don't telephone holler upwards rs.next() together with straight telephone holler upwards rs.getInt(columnName) together with getIndex(), you volition acquire next error, thus ever telephone holler upwards rs.next() earlier calling whatever getXXX() method.

java.sql.SQLException: Before start of effect set

        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073)

        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)

        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)

        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)

        at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:841)

        at com.mysql.jdbc.ResultSetImpl.getInt(ResultSetImpl.java:2674)

That’s all on How to connect to MySQL database from Java program. We convey seen measuring past times measuring details to connect MySQL 5.5. database together with executed SELECT query against it. We convey every bit good touched base of operations on roughly of the mutual SQLException which comes inwards JDBC code during connexion or reading effect via ResultSet.

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Class Inwards Coffee Together With Object Oriented Programming Linguistic Communication - Video Tutorial

Class together with Object are 2 pillars of Java programming language. There are multiple ways you lot tin plow over the sack clitoris Class inwards Java, for someone  Class is a user defined type, for others it's designing to practice objects together with for few of other it's only a agency to model existent basis entity. Questions come upwards why practice nosotros involve Class inwards Java, good 1 matter I tin plow over the sack intend of is to combine multiple types into 1 structure. Class together with Object along amongst nub OOPS concept e.g. Abstraction, Encapsulation, Inheritance and Polymorphism is the kickoff matter whatsoever Java programmer learn. I convey only finished a basic Java presentation on Class for beginners which gives an introduction of What is Class inwards Java together with details about of import details virtually Java Classes.

Class inwards Java - Things to know

Following are about primal matter virtually Class inwards Java programming linguistic communication for beginners :

1) Class is represented using class keyword

2) There are 2 kinds of class, acme marker together with nested shape inwards Java.

3) According to Java convention, the get upwards of the shape should start amongst working capital missive of the alphabet letter.



4) Unlike C structures which are analogous to class, Java classes tin plow over the sack comprise non solely variables but besides methods which operate on those fields.

5) The shape is the smallest unit of measurement of modular code, functionality inwards Java is presented inwards damage of class.

6) As per SRP (Single Responsibility Principle)  SOLID designing principle, a shape should solely correspond 1 matter together with at that spot should non endure to a greater extent than than 1 argue to alter a class. Well designed classes are primal for loosely coupled together with modular code inwards Java.

6) Class doesn't practice anything special, it's only defined construction together with object practice all the things.

See my presentation on What is shape inwards Java for to a greater extent than details



That's all on What is Class inwards Java programming language, at that spot are a lot to a greater extent than details which nosotros volition utter over inwards the farther post.  The best agency to larn Class together with Object is to model about existent basis things e.g. Person, Student, Employee etc.

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Can Abstract Bird Convey Constructor Inward Coffee - Interview Question

Yes, an abstract bird tin possess got a constructor inwards Java. You tin either explicitly render a constructor to abstract bird or if y'all don't, the compiler volition add together default constructor of no declaration inwards abstract class. This is truthful for all classes in addition to it too applies to an abstract class. For those who desire to recollect what is an abstract bird inwards Java, it's a bird which tin non endure instantiated amongst new() operator or whatever other ways. In guild to purpose an abstract bird inwards Java,  You involve to extend it in addition to render a concrete class. Abstract bird is usually used to define a base of operations bird for a type hierarchy amongst default implementation, which is applicable to all modest classes. By the way, difference betwixt interface in addition to abstract bird inwards Java is too i of the pop in addition to tricky Java questions in addition to should endure prepared good for Java interviews.  


Can nosotros declare constructor on abstract bird inwards Java is follow-up of other  similar Java interview questions e.g. Can nosotros override static method inwards Java?. Why does interviewer inquire this questions? Mainly because, trying to confuse programmer amongst the fact that since an abstract bird tin non endure instantiated, why abstract bird needs constructor. In this Java Interview interrogation article nosotros volition run across that Abstract bird tin possess got a constructor inwards Java.

Why tin an abstract bird possess got a constructor inwards Java?

Now if nosotros say nosotros tin non practise an instance of an abstract bird in addition to then why practise Java adds a constructor inwards the abstract class. One of the reasons which brand feel is  when whatever bird extends an abstract class, the constructor of sub bird volition invoke the constructor of super bird either implicitly or explicitly. This chaining of constructors is i of the reasons abstract bird tin possess got constructors inwards Java.

Here is an instance Java program, which proves that abstract bird tin possess got constructors inwards Java :

/**  * Simple Java programme to examine that abstract bird tin possess got constructor inwards Java.  * @author http://java67.blogspot.com  */ public class AbstractConstructorTest {      public static void main(String args[]) {        Server server = new Tomcat("Apache Tomcat");        server.start();     } }  abstract class Server{     protected final String name;         public Server(String name){         this.name = name;     }         public abstract boolean start(); }  class Tomcat extends Server{         public Tomcat(String name){         super(name);     }      @Override     public boolean start() {        System.out.println( this.name + " started successfully");        return true;     }     }  Output: Apache Tomcat started successfully  

In this instance Java program, nosotros possess got an abstract bird Server, which has a constructor amongst i parameter, which accepts the name. Subclass provides that advert to superclass piece creating a concrete instance of Server in addition to overriding abstract method starts(). Since this programme compiles in addition to run fine y'all tin definitely say abstract bird tin possess got constructors inwards Java.

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Difference Betwixt Jit Too Jvm Inwards Coffee - Interview Question

The principal divergence betwixt JIT together with JVM is that JIT is component division of JVM itself together with its principal component division is to ameliorate the functioning of JVM past times direct compiling about hot code (code which executes inwards a higher house a certainly threshold) into native instruction. JIT stands for Just In fourth dimension compilation together with JVM stands for Java Virtual Machine. JVM is a virtual car used inwards Java programming platform to execute or run Java programs. The principal wages of JVM is that JVM  makes Java platform-independent past times executing bytecodes. Java source code is compiled into course of teaching files, which contains bytecode. These byte codes are together with thence executed past times JVM. Now hither comes JIT. Since the execution of bytecode is slower than the execution of car linguistic communication code, because JVM starting fourth dimension needs to interpret bytecode into car linguistic communication code.

JIT helps JVM hither past times compiling currently executing byte code into car language. JIT too offers caching of compiled code which number inwards improved functioning of JVM.

By the agency divergence betwixt JVM together with JIT is too a good Java interview question to ask. Well, this is only a uncomplicated explanation, JIT is lot to a greater extent than complex than this. There are sophisticated algorithm which helps JIT to selection virtually executed code for compiling into car code.

Earlier nosotros own got seen difference betwixt JRE together with JDK together with inwards this postal service nosotros volition sympathize difference betwixt JVM together with JIT. Let's run into adjacent department for to a greater extent than divergence betwixt JIT vs JVM.

JVM vs JIT

Just inwards fourth dimension compiler or JIT is an integral constituent of Java Virtual Machine along amongst Garbage collector, which equally advert advise does Just inwards fourth dimension compilation. It is capable of compiling Java code direct into car language, which tin plough over the axe greatly ameliorate functioning of Java application.

By the way, its non guaranteed that which code volition live compiled together with when. JIT unremarkably compile hot code inwards Hotspot JVM in ane lawsuit its execution cross certainly restrict e.g. a method volition live converted into car linguistic communication if it is called to a greater extent than than 10K times etc.

Here are couplet of to a greater extent than differences betwixt JVM together with JIT inwards Java programming platform :

1) Main divergence betwixt JVM together with JIT is at that topographic point purpose, principal finish of JVM is to render platform independence acre objective of JIT is to ameliorate functioning of JVM, past times compiling to a greater extent than code into car language. Just buy the farm along inwards heed that this compilation too takes time, thence translating all code into native code is non worth doing. That's why JIT by together with large compile ofttimes used code into native code.

2) Another divergence betwixt JIT together with JVM is that, JIT is component division of JVM. One event of JIT is Oracle's Hotspot JIT which comes amongst Hotspot JVM. It is called hotpost because its Just inwards fourth dimension compiler compiles solely hot code into native language, code which execute 90% of time.

There is threshold setup, if about code executes to a greater extent than than that threshold together with thence it larn eligible for only inwards fourth dimension compiled. By the way, Hotspot is non the solely JVM which contains Just inwards fourth dimension compilers, at that topographic point are others JVM equally good e.g. Oracle's master JRockit one. 

3) At last, JVM is older concept than JIT. JIT genuinely invented to ameliorate functioning of JVM afterward years of initial loose of Java, acre Java virtual car was component division of initial Java release. 

That's all on difference betwixt JVM together with JIT inwards Java. As I said, JIT is component division of JVM together with used to ameliorate JVM functioning past times dynamically compiling or translating Java byte codes into native car linguistic communication code during execution time.

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