How to Convert Double to String to Double in Java Program with Example

Many scenarios come in day to day Java programming when we need to convert a Double value to String or vice versa. In my earlier article we have seen how to convert String to Integer and in this article, we will first see how to convert double to String and the later opposite of  that from String to double. One important thing to note is Autoboxing which automatically converts primitive type to Object type and only available from Java 5 onwards. This conversion example assumes the code is running above Java 5 version and actually tested in JDK 1.6, which makes it unable to pass Double object when the method is expecting double primitive value likeString.valueOf(double d) which expect a double value.

How to Stop Thread in Java Code Example

The thread is one of the important Classes in Java and multithreading is the most widely used feature, but there is no clear way to stop Thread in Java. Earlier there was a stop method exists in Thread Class but Java deprecated that method citing some safety reason. By default, a Thread stops when the execution of run() method finishes either normally or due to any Exception. In this article, we will How to Stop Thread in Java by using a boolean State variable or flag.

What is static import in Java 5 with Example

Static import in Java allows to import static members of the class and use them, as they are declared in the same class. Static import is introduced in Java 5 along with other features like Generics, Enum, Autoboxing and Unboxing and variable argument methods. Many programmers think that using static import can reduce code size and allow you to freely use static field of external class without prefixing class name on that. For example without static import you will access static constant MAX_VALUE of Integer class as Integer.MAX_VALUE but by using static import you can import Integer.MAX_VALUE and refer it as MAX_VALUE.

How to use multiple JQuery UI Date Picker or Datepicker in HTML or JSP page

We often need to use multiple JQuery date picker in one HTML or JSP page, classical example is online flight booking for return trips, where you need to pick departure date and arrival date from two separate date pickers. While designing HTML forms either statically or dynamically using JSP, you may want to associate date picker with multiple input text field, paragraph or any other HTML elements. By using JQuery UI and some help from CSS ID and class selector, we can easily use multiple date pickers in one HTML page. All you need to do is, declare a CSS class says .datepicker and apply that class to all HTML elements which need date picker, for example, we have associated date picker with 4 input text fields, which has .datepicker class.

What is difference between java.sql.Time, java.sql.Timestamp and java.sql.Date - JDBC interview Question

Difference between java.sql.Time, java.sql.Timestamp and java.sql.Date  is the most common JDBC question appearing on many core Java interviews. As JDBC provides three classes java.sql.Date, java.sql.Time and java.sql.Timestamp to represent date and time and you already have java.util.Date which can represent both date and time, this question poses a lot of confusion among Java programmer and that’s why this is one of those tricky Java questions which is tough to answer. It becomes really tough if the differences between them are not understood correctly.

How to replace NULL with Empty String in SQL Server? ISNULL() vs COALESCE() Examples

We often need to replace NULL values with empty String or blank in SQL e.g. while concatenating String. In SQL Server, when you concatenate a NULL String with another non-null String the result is NULL, which means you lose the information you already have. To prevent this, you can replace NULL with empty String while concatenating. There are two ways to replace NULL with blank values in SQL Server, function ISNULL(), and COALESCE(). Both functions replace the value you provide when the argument is NULL like ISNULL(column, '') will return empty String if the column value is NULL.

Eclipse shortcut to System.out.println in Java program - Tips

Eclipse IDE provides quick shortcut keys to print System.out.println statement in Java but unfortunately not every Java programmers are familiar with that.  Even programmers with 3 to 4 years of experience sometimes don't know this useful Eclipse shortcut to generate System.out.println messages.  This Eclipse tip is to help those guys. Let me ask you one question, How many times you type System.out.println in your Java program?  I guess multiple times while doing programming, debugging, and testing small stuff.  System.out.println is the most preferred way to print something on console because it doesn’t require setups like configuring Log4J or java.util.Logger .

Java program to calculate area of Triangle - Homework, programming exercise example

Calculate the area of Triangle in Java

Write a Java program to calculate Area of Triangle, accept input from User, and display output in Console is one of the frequently asked homework questions. This is not a tough programming exercise but a good exercise for beginners and anyone who has started working in Java. For calculating the area of a triangle using formula 1/2(base*height), you need to use arithmetic operators. By doing this kind of exercise you will understand how arithmetic operators work in Java, subtle details which affect calculation like precedence and associativity of the operator, etc.

How to Implement Binary Search Tree in Java? Example

A binary search tree or BST is a popular data structure that is used to keep elements in order. A binary search tree is a binary tree where the value of a left child is less than or equal to the parent node and the value of the right child is greater than or equal to the parent node. Since its a binary tree, it can only have 0, 1, or two children. What makes a binary search tree special is its ability to reduce the time complexity of fundamental operations like add, remove, and search, also known as insert, delete and find. In a BST, all these operations (insert, remove, and find) can be performed in O(log(n)) time.

5 ways to add multiple JAR in to Classpath in Java

How to add JAR file to Classpath in Java

Adding JAR into classpath is a common task for Java programmer and different programmer do it on different way. Since Java allows multiple ways to include JAR file in classpath, it becomes important to know pros and cons of each approach and How exactly they work. There are 5 ways to add  jars on into classpath in Java some of them we have already seen in  How classpath works in Java and How to set Path in Java. In this post we will revisit some of those techniques and explore Java 1.6 wildcard to add multiple JAR into classpath. By the way here is 5 ways to add JAR file into classpath. In short knowledge of Path, Classpath and Classloaders are must for any Java programmer, not only from knowledge point of view but also to successfully debug and resolve issues related to Classpath e.g. NoClassDefFoundError and java.lang.ClassNotFoundException  in Java.

What is Iterator and ListIterator in Java Program with Example - Tutorial Code Sample

Iterator in Java is nothing but a traversing object, made specifically for Collection objects like List and Set. we have already aware about different kind of traversing methods like for-loop ,while loop,do-while,for each lop etc,they all are  index based traversing but as we know Java is purely object oriented language there is always possible ways of doing things using objects so Iterator is a way to traverse as well as access the data from the collection. Even with traversing with object we have Enumeration, Iterator and ListIterator in Java which we will in this Java Iterator tutorial.

Regular Expression in Java to check numbers in String - Example

Regular Expression to check numeric String

In order to build a regular expression to check if String is number or not or if String contains any non-digit character or not you need to learn about character set in Java regular expression, Which we are going to see in this Java regular expression example. No doubt Regular Expression is a great tool in developer arsenal and familiarity or some expertise with regular expression can help you a lot. Java supports regular expression using java.util.regex.Pattern and java.util.regex.Matchter class, you can see a dedicated package java.util.regex for a regular expression in Java. Java supports regex from JDK 1.4, which means well before Generics, Enum, or Autoboxing.

Difference between private, protected, public and package modifier or keyword in Java

private vs public vs protected vs package in Java

Java has four access modifier namely private, protected and public. package level access is default access level provided by Java  if no access modifier is specified. These access modifiers are used to restrict accessibility of a class, method or variable on which it applies. We will start from private access modifier which is most restrictive access modifier and then go towards public which is least restrictive access modifier, along the way we will see some best practices while using access modifier in Java and some examples of using private and protected keywords.

Difference between Truncate and Delete command in SQL - Interview Questions with Example

Truncate and delete in SQL are two commands which are used to remove or delete data from a table. Though quite basic in nature both SQL commands can create a lot of trouble until you are familiar with details before using it. The difference between Truncate and delete are not just important to understand perspective but also a very popular SQL interview topic which in my opinion a definite worthy topic. What makes them tricky is the amount of data. Since most Electronic trading system stores, large amounts of transactional data, and some even maintain historical data, a good understanding of delete and the truncate command is required to effectively work in that environment.

How to convert decimal to binary, octal and hex String in Java Program

This article is a simple Java program that converts the decimal number to binary, octal, and hexadecimal format. When it first came into my mind I thought I would probably need to write whole code to convert decimal to various other radix or base numbers but when I looked Integer class and saw these two ways of converting decimal to binary etc I was simply amazed. It’s indeed extremely easy to do this in java and you can also write this program or use it is.

10 Example Queries of SQL Select Command

The Select command in SQL is one of the most powerful and heavily used commands. This is I guess the first command anyone learns in SQL even before CREATE which is used to create a table in SQL. SELECT is used in SQL to fetch records from database tables and you can do a lot many things using Select. For example, you can select all records, you can select few records based on the condition specified in WHERE clause, select all columns using the wild card (*) or only selecting a few columns by explicitly declaring them in a query.

How to Use Locks in Multi-threaded Java Program

Many Java programmers confused themselves like hell while writing multi-threaded Java programs like where to synchronized? Which Lock to use? What Lock to use etc. I often receive a request to explain how to use Locks in Java, so I thought to write a simple Java program, which is multi-threaded and uses a rather new Lock interface. Remember Lock is your tool to guard shared resources which can be anything e.g. database, File system, a Prime number Generator, or a Message processor. Before using Locks in Java program, it’s also better to learn some basics. Lock is an interface from java.util.concurrent package. It was introduced in JDK 1.5 release as an alternative of the synchronized keyword.

Java Program to get input from User from Console or command line- Example Tutorial Code

How to get input from user in Java from command line or console is one of the common thing ,every one started learning Java looks for. It’s second most popular way of starting programming after HelloWorld in Java. There are so many ways to get input from User in Java including command line and Graphical user interface. For beginner simpler the example, better it is. first and foremost way of getting input from user is String[] passed to main method in Java but that only work for one time requirement and its not interactive. Another way of getting input from User is involving IO classes like InputStream to read from console or command line which can be little complicated for true beginner.

What is Double Brace Initialization in Java? Anti Pattern Example

Double brace initialization is a Java idiom to initialize a Collection like a list, set and map at the time of declaration. At times, you need a list of fixed elements e.g. supported products, supported currencies or some other config, and on the spot initialization reduces line of code and improves readability. Double brace initialization idiom becomes popular because there is no standard way to create and initialize Collection at the same time in Java. Unfortunately, unlike another language, Java doesn't support collection literals yet. Due to this limitation, creating an unmodifiable List with small numbers of elements requires many lines of code involving creating list, repeatedly calling add() method to add those elements and then finally wrapping it into unmodifiable list as shown below :

What is Class in Java Programming with General Example

When I first about Class in Java I just thought what is this Class in Java and from that date to now Whenever we talk about java its really incomplete without classes, every one who are little bit familiar with java knows it’s purely object oriented language means every thing we discuss in java as object .so its very important for learner or anyone who is keen to know about java should know about java class then only they can move forward on java world.

In this article we will see what Java Class, Example of Class in Java is and what makes a Java Class including members, field and method.

Google Dart: New Programming language to replace JavaScript

Google Dart: Structured Web Programming language 

Google has launched its much-awaited mysterious DART web programming language. Ahh, another programming language…, why does google launched a new language Google DART? What I read from the web is that Google is trying to replace JavaScript as the main web scripting language. Over the years from Netscape Era JavaScript has evolved, formed a large based of Developers and has existing codes, framework, and utilities, so I am not sure how far Google DART can go but this is a serious attempt to replace JavaScript much in the line of Chrome which was launched to replace Internet Explorer and What we see now is they are living happily with their own market share though Chrome is growing and snatching market share from other browsers.

Effective Java, 3rd Edition - Covers JDK 7, 8, and 9 - Must Read Book for Java Programmers

Hello guys, I have an interesting news to share with you today. After a long wait of almost 10 years, the Effective Java 3rd edition is finally coming this year, hopefully, December 2017. The Effective Java 2nd Edition was released in May 2008 and updated for Java SE 6, but it been, good 10 years now and there is a lot of interest from Java developers around the world for Effective Java 3rd edition after Java SE 8 release and I am very happy to inform you guys that, finally, all our wishes are granted and Effective Java 3rd edition is set to arrive this year. It will not only cover Java 9 release but also all the changes from Java 7 and Java 8.

How to write build.xml and run build in Apache ANT

This is the second article on Apache ANT tutorials for beginners series As I have always said that I like the short , clear and concise tutorial which tells about few concept but in a clear and concise manner and put weight on fundamentals . I try to adopt same theory while writing my blog post while writing my experience coupled with the concept which is important for a software developer point of view.

SQL Server JDBC Error: The TCP/IP connection to the host Failed

I had installed SQL SERVER 2014 Express edition and I was trying to connect to SQL SERVER from Java program using JDBC, but I was repeatedly getting the following error:

com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host localhost, port 1433 has failed. Error: "connect timed out. Verify the connection properties. Make sure that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port. Make sure that TCP connections to the port are not blocked by a firewall.".Error while closing connection !!null

Right way to Close InputStream and OutputStream in Java

For some unknown reasons many Java programmers are not very comfortable with IO package. I don't know why, but I have found them much more comfortable with java.lang and java.util than java.io. One possible reason of this could be that, writing IO code require a bit of C++ like programming, which involves doing clean-up, releasing resources once done etc. Since Java made coding a lot easier by taking care of memory management, unknowingly it also introduced bad practice of not releasing resource after use e.g. database connections, socket connection, files, directory, printers, scanners or any other scarce resource.

How SubString method works in Java - Memory Leak Fixed in JDK 1.7

Substring method from String class is one of most used method in Java, and it's also part of an interesting String interview question  e.g. How substring works in Java or sometime asked as how does substring creates memory leak in Java. In order to answer these questions, you knowledge of  implementation details is required. Recently one of my friend was drilled on substring method in Java during a Java interview, he was using substring() method from long time, and of course all of us has used this, but what surprises him was interviewer's obsession on Java substring, and deep dive till the implementation level.

How to build project using Apache ANT ? ANT Build Tutorials for Beginners

Apache Ant tutorials for beginners

Hi Guys, today I would like to share some of my experience while working with ant build tool in form of short ant tutorials, ant is one tool which has gained its place in almost everywhere, it’s integral part of any project’s build system and provide foundation for complex, extensible build environment. I have been using ANT from my early programming days and I have seen some of the best designed build environments around ANT. In these ant tutorials for beginners we will see what is ant build tool? How to use ANT for building project? Fundamentals of ANT build tool, setting up ant build environment etc. I have created a series of ant tutorials and you can check next part of ant tutorials by following links ant tutorial part 2 and ant tutorial part 3. 

20 Questions You can ask to Interviewer in Programming Job Interviews?

From the first round to HR round, from telephonic to face-to-face, in almost all kind of programming interviews, there will be a time when Interviewer will give you a chance to ask questions. Many programmers are too concern about asking questions, and they politely decline ; Well it's your chance to learn about the Job you are going to do, and you shouldn't let this opportunity goes away. The interviewer, also judges you by your questions; a good, thoughtful, positive question can create the great impression on Interviewer's mind. It also shows that  the interest of a candidate for a Job.

10 Programming Best Practices to Name Variables, Methods, Classes and Packages in Java

What's in a name? "A rose by any other name would smell as sweet" is a famous quote from William Shakespeare's classic Romeo and Juliet, but sorry to say, name matter a lot in programming and coding.  It's also said that code is the best document for any software because any other document or comments can become outdated quickly, but code will always tell you the truth. And, If code is the best document then names are the most critical element of it. Every effort, small or big, invested while naming variables or methods, pays in both the short term and long term. In fact, if you ask me just one coding practice to follow, I would definitely recommend giving meaningful names to your variables and methods.

Top 10 Java String interview Question answers - Advanced

10 Java String interviews Question answers
String interview questions in Java is one of Integral part of any Core Java or J2EE interviews. No one can deny the importance of String and how much it is used in any Java application irrespective of whether its core Java desktop application, web application, Enterprise application or Mobile application. The string is one of the fundamental of Java programming language and correct understanding of String class is a must for every Java programmer. What makes String interview questions in Java even more interesting is the special status of String in terms of features and privileges it has, like the + operator is kind of overloaded to perform String concatenation despite the fact that Java does not support operator overloading. There is a separate String pool to store String literal etc.

How to Set Path for Java Unix Linux and Windows

PATH is one of fundamental Environment variable on shell or DOS but it’s commonly associated with Java mainly because if we try to run a java program which doesn't include Java executable in PATH then we say PATH is not set for Java and we need to set the path for Java. I have also seen the developer getting confused over path and classpath in java. Though both path and classpath provide run-time settings for any java environment which is required to compile and executes Java program they are completely different to each other.

What is Inheritance in Java and OOPS Tutorial - Example

Inheritance in Java is an Object oriented or  OOPS concepts, which allows to emulate real world Inheritance behavior, Inheritance allows code reuse in Object oriented programming language e.g. Java. Along with Abstraction, Polymorphism and Encapsulation, Inheritance forms basis of Object oriented programming. Inheritance is implemented using extends keyword in Java and When one Class extends another Class it inherit all non private members including fields and methods. Inheritance in Java can be best understand in terms of Parent and Child class, also known as Super class and Sub class in Java programming language.

Database Website to Run and Practice SQL Query Online for FREE - SQLFiddle

Another day, I was looking for a website to execute SQL query online, since I have uninstalled Microsoft SQL Server because of memory and CPU constraint and I don't want to install it again, just for executing another query. Also, installing database is pain, it takes time and eats up lots of resources e.g. RAM memory, CPU, etc; Given so many databases to work with e.g. Oracle, MySQL, Sybase, PostgreSQL, and SQLLite, it's not really possible to have all of them in your poor laptop. Fortunately, my search leads me to this wonderful site called SQLFiddle, this is what exactly I wanted. This site offers support for a lot of popular databases, allows you to build your database schema online, and execute SQL query on the fly.

How to convert java.util.Date to java.sql.Date - JDBC Example

You often need to convert java.util.Date to java.sql.Date if you are storing dates in database e.g. SQL SERVER or MySQL. Since JDBC has their own data types for date and time e.g. java.sql.Date, java.sql.Time and java.sql.TimeStamp to match with database date, time and date-time types, you cannot pass a java.util.Date directly. All methods which are suppose to store dates e.g. setDate(paramName, paramValue) expects java.sql.Date, so it becomes essential to know how to convert java.util.Date to java.sql.Date in JDBC. You would be surprised to know that java.sql.Date is a subclass of java.util.Date and all it does is suppress or remove time-related fields from java.util.Date.

What is PriorityQueue or priority queue data structure in Java with Example - Tutorial

PriorityQueue is an unbounded Queue implementation in Java, which is based on priority heap. PriorityQueue allows you to keep elements in a particular order, according to there natural order or custom order defined by Comparator interface in Java. Head of priority queue data structure will always contain least element with respect to specified ordering. For example, in this post, we will create a PriorityQueue of Items, which are ordered based upon there price, this will allow us to process Items, starting from lowest price. Priority queue is also very useful in implementing Dijkstra algorithm in Java. You can use to PriorityQueue to keep unsettled nodes for processing.

How to override hashcode in Java example - Tutorial

Equals and hashcode methods are two primaries but yet one of the most important methods for java developers to be aware of. Java intends to provide equals and hashcode for every class to test equality and to provide a hash or digest based on the content of the class. The importance of hashcode increases when we use the object in different collection classes which works on hashing principle e.g. hashtable and hashmap. A well-written hashcode method can improve performance drastically by distributing objects uniformly and avoiding a collision.