7 jQuery Selectors Examples for Beginners - Tutorial

jQuery selectors are like CSS Selectors, which allow you to find or select an element from the DOM tree. When HTML pages loaded in a browser like Chrome, Firefox, or Internet Explorer, the browser creates a tree-like structure is known as Document Object Model or DOM. JavaScript and jQuery allow you to play with this DOM i.e. selecting elements from DOM, traversing through DOM, going from one element to another, selecting a list of elements from DOM, adding or removing elements from DOM, etc. In order to apply most of the jQuery functions, available in the jQuery object, we first need to select HTML elements or tags, on which we want to apply those functions, jQuery selector allows you to choose those elements.

How to Create Read Only List, Map and Set in Java – UnModifiable Collection Example

Read-only List, Map and Set in Java
A read-only List means a List where you can not perform modification operations like add, remove or set. You can only read from the List by using get method or by using Iterator of List, This kind of List is good for a certain requirement where parameters are final and can not be changed. In Java, you can use Collections.unModifiableList() method to create read-only List , Collections.unmodifiableSet() for creating read-only Set like read-only HashSet and similarly creating a read-only Map in Java, as shown in below example. Any modification in the read-only List will result in java.lang.UnSupportedOperationException in Java.  

How to Load Resources from Classpath in Java with Example

Classpath in Java is not only used to load .class files, but also can be used to load resources e.g. properties file, images, icons, thumbnails, or any binary content. Java provides API to read these resources as InputStream or URL. Suppose, you have a properties file inside config folder of your project, and you want to load that properties file, how do you do that? Similarly, you have icons and thumbnails for your web applications on icons directory of your project, how do you load them? The answer is by using java.lang.Class' getResource() and getResourceAsStream() method. These method accepts the path of resource as String and returns URL and InputStream respectively.

How to sort a Map by keys in Java 8 - Example Tutorial

In the last article, I have shown you how to sort a Map by values in Java 8, and in this tutorial, you will learn how to sort a Map by keys lik a HashMap, ConcurrentHashMap, LinkedHashmap, or even Hashtable. Theoretically, you cannot sort a Map because it doesn't provide any ordering guarantee. For example, when you iterate over a HashMap, you don't know in which order entries will be traversed because HashMap doesn't provide any ordering. Then, how can you sort a Map which doesn't support order? Well, you can't and that's why you only sort entries of HashMap but you don't store the result back into HasMap or any other Map which doesn't support ordering. If you do so, then sorting will be lost.

Default, Defender or Extension Method of Java 8 with Example

Java 8 now allows you to add non-abstract method implementations to interfaces by utilizing the default and static keyword. Methods with default keyword are known as default methods or defender methods in Java. Before Java 8, it was virtually impossible to change an interface once published. Any change e.g. the addition of a new method would have broken all clients. That's why when Java 8 decided to switch to internal iterator implementation using forEach() method, they face a daunting challenge of breaking all implementation of Iterable interface. Since backward compatibility is a top priority for Java engineers, and it wasn't practical to break all clients, they came up with the idea of the default method.

How to Calculate Difference between two Dates in Java (In Days)

If you are not running on Java 8, then there are two ways to calculate the difference between two dates in Java in days, either by using standard JDK classes e.g. java.util.Date and java.util.Calendar or by using the joda-time library. Unfortunately, Java's old Date and Calendar API is buggy and not intuitive, so many of us by default use Joda for all date and time arithmetic. In this example, you will learn how to find  the number of days between today and any date entered by a user using Joda, as well as without using any third party library. When I first time face this problem, I thought what's a big deal about finding the difference between dates? If you can convert Date to milliseconds then finding a number of days, months or years are just a matter of simple arithmetic, but I was WRONG. I was not thinking about real world date and time nuisance like leap seconds, leap years, and daylight saving time.

3 Ways to Read File line by line in Java 8? Examples

Java 8 has added a new method called lines() in Files class which can be used to read a file line by line in Java. The beauty of this method is that it reads all lines from a file as Stream of String, which is populated lazily as the stream is consumed. So, if you have a huge file and you only read the first 100 lines then the rest of the lines will not be loaded into memory, which results in better performance. This is slightly different from than Files.readAllLines() method (which reads all lines into a List) because this method reads the file lazily, only when a terminal operation is called on Stream e.g. forEach(), count(), etc. By using count() method you can actually count a number of lines in files or number of empty lines by filtering empty lines.

How to read file line by line in Java - BufferedReader Scanner Example Tutorial

Line by Line reading in Java using BufferedReader and Scanner
There are multiple ways to read file line by line in Java. Most simple example of reading file line by line is using BufferedReader which provides method readLine() for reading file. Apart from generics, enum and varargs Java 1.5  has also introduced several new class in Java API one of the utility class is Scanner, which can also be used to read any file line by line in Java. Though BufferedReader is available in Java from JDK 1.1,  java.util.Scanner provides more utility methods compared to BufferedReader. Scanner has method like hasNextLine() and nextLine() to facilitate line by line reading of file's contents. nextLine() returns String similar to  readLine() but the scanner has more utility methods like nextInt(), nextLong() which can be used to directly read numbers from a file instead of converting String to Integer or other Number classes.

How to Create Thread Pool in Java using Executor Framework - Example Tutorial

Java 1.5 introduced a Thread pool in Java in the form of an Executor framework, which allows Java programmers to decouple submission of a task to the execution of the task. If you are doing server-side programming in Java than the Thread pool is an important concept to maintain scalability, robustness, and stability of the system. For those, who are not familiar with thread pool in Java or concept of thread pool here is a one-liner, Thread pool in Java is a pool of worker threads, which is ready to perform any task given to them, mostly in the form of implementation of Runnable or Callable interface.

Top 50 Java Programs from Coding Interviews

Coding is an integral part of any programming job interviews, and Java development interviews are no exception. I would even suggest you should never hire anyone without testing their coding skill, coding is also an art, and more often than a good code is an excellent developer as well. If you look at tech giants like Amazon, Facebook, and Google they thoroughly test the coding skill of any developer they hire, notably Amazon who first send online coding exercises to filter Java programmers who can code. This online test usually gives you requirements and ask you to write a program in a limited time, usually 2 to 3 hours. The application should meet the output provided by the exercise itself. These type of tasks are very tough to crack if you don't have excellent coding skill.

Arithmetic overflow error converting numeric to data type numeric in SQL Server

This error comes when you try to store an out-of-range floating point value into a numeric variable. For example, if your NUMERIC or DECIMAL variable is defined as NUMERIC(5,2) than the maximum value it can hold is 999.99, if you try to store something like 1000.00 then it will throw "Arithmetic overflow error converting numeric to data type numeric". One of the common reasons for this error is the ignorance and misunderstanding of the NUMERIC data type. For example, many SQL Server DBAs and developers think that a NUMERIC(5,2) variable can hold a 7 digit floating point number where 5 digit is before the decimal and 2 digits are after the decimal. This is wrong.

How to Read XML File as String in Java? 3 Examples

Suppose you have an XML file and you just want to read and display the whole file as String in Java, may be for debugging purpose. If you are wondering how to do that in Java, well there are many ways to read XML as String in Java. You can do it in one line if you are fine with using an open source library or you can do it in a couple of lines of code in core Java as well. Since an XML file is also a file, you can use BufferedReader or FileInputStream to read the content of an XML file as String by using the techniques, I have discussed in my earlier post 3 ways to convert InputStream to String in Java. But this post is about a new library called jcabi-xml which makes working with XML file really easy. You can parse the XML file using XPath expression, you can do XSL transformation, XSD schema validation and you can even parse whole XML file as String in just a couple of lines of code.

Difference between get and load in Hibernate

get vs load in Hibernate
Difference between get and load method in Hibernate is one of the most popular questions asked in Hibernate and spring interviews. Hibernate Session class provides two methods to access object e.g. session.get() and session.load() both looked quite similar to each other but there are subtle differences between load and get method which can affect the performance of the application. The main difference between get() vs load method is that get() involves database hit if an object doesn't exist in Session Cache and returns a fully initialized object which may involve several database calls while load method can return proxy in place and only initialize the object or hit the database if any method other than getId() is called on persistent or entity object.

How to convert String or char to ASCII values in Java

You can convert a character e.g. 'A' to its corresponding ASCII value 65 by just storing it into a numeric data type e.g. byte, int or long as shown below :

int asciiOfA = (int) 'A';

Here casting is not necessary, simply assigning a character to integer is enough to store ASCII value of character into an int variable, but casting improves readability. Since ASCII is 7-bit character encoding, you don't even need an integer variable to store ASCII values, byte data type in Java, which is 8 bits wide is enough to store ASCII value of any character.  So you can also do like this :
byte asciiOfB = 'B'; // assign 66 to variable

What is Autoboxing and Unboxing in Java – Example Tutorial and Corner cases

What is Autoboxing in Java
Autoboxing and unboxing are introduced in Java 1.5 to automatically convert the primitive type into boxed primitive( Object or Wrapper class). autoboxing allows you to use primitive and object type interchangeably in Java in many places like an assignment, method invocation etc. If you have been using Collections like HashMap or ArrayList before Java 1.5 then you are familiar with the issues like you can not directly put primitives into Collections, instead, you first need to convert them into Object only then only you can put them into Collections. Wrapper class like Integer, Double and Boolean helps for converting primitive to Object but that clutter the code. With the introduction of autoboxing and unboxing in Java, this primitive to object conversion happens automatically by Java compiler which makes the code more readable.

9 Difference between TCP and UDP Protocol - Java Network Interview Question

TCP and UDP are two transport layer protocols, which are extensively used on the internet for transmitting data from one host to another. Good knowledge of how TCP and UDP works is essential for any programmer. That's why the difference between TCP and UDP is one of the most popular programming interview questions. I have seen this question many times on various Java interviews, especially for server-side Java developer positions. Since FIX (Financial Information Exchange) protocol is also a TCP based protocol, several investment banks, hedge funds, and exchange solution provider looks for Java developer with good knowledge of TCP and UDP. Writing fix engines and server side components for high-speed electronic trading platforms needs capable developers with a solid understanding of fundamentals including data structure, algorithms, and networking.

How to find duplicate words in Java String? [Solution]

Problem:  Write a Java program to print the duplicate words from a given statement e.g. if the given String is "Java and JavaScript are totally different, JavaScript follows Java" then your program should print "Java" and "JavaScript" because those two are 2 duplicate words from given String. You need to consider all cases e.g. given String can be null, empty, may or may not contain any duplicate words, but for simplicity, you can assume that sentence will always in English and only use ASCII characters, alphabets, and numerals, no special character.

How to Find Largest of Three Integers in Java - Algorithm, Logic Example

One of the classical programs to build programming logic is, write a program to find the largest of three numbers. I am sure many of you have already done this exercise in a variety of languages including C, C++, C#, JavaScript, Perl, Ruby, PHP, etc. This time we will do it in Java. We will first learn the logic by understanding the flowchart of the largest of three numbers and then we will implement solution using the ternary operator in Java. I love this program for its sheer simplicity and how it can help beginners to build logic. As always, you are not allowed to use any library function which can solve this problem directly, your main task is to build logic using primitive language tools e.g. operators.

How to solve java.lang.classnotfoundexception sun.jdbc.odbc.jdbcodbcdriver in Java 8

java.lang.classnotfoundexception sun.jdbc.odbc.jdbcodbcdriver exception comes in Java 8 because it has removed the JDBC ODBC bridge driver class "sun.jdbc.odbc.jdbcodbcdriver" from JDK and JRE. This class is required to connect any database using Object database connectivity driver e.g. Microsoft Access, but unfortunately, you cannot use it from JDK 8 onward. In order to solve this error, just use the Jackcess library or a commercial driver like HXTT. Normally, in pre-Java 8 world, java.lang.classnotfoundexception sun.jdbc.odbc.jdbcodbcdriver error comes when you try to connect to the Microsoft Access database from Java using JDBC and JDBC ODBC bridge driver is not available in the classpath.

Write a Program to Find all Armstrong number in the range of 0 and 9999 - Example

An Armstrong number of three digits is an integer such that the sum of the cubes of its digits is equal to the number itself. For example, 153 is an Armstrong number, since 1**3 + 5**3 + 3**3 = 153, 371 is an Armstrong number since 3**3 + 7**3 + 1**3 = 371. Along with usual beginner exercises e.g. calculating factorial, reversing a string, or calculating prime numbers, this is a good exercise to build programming logic. It teaches you basic programming technique of how to use the operator for something which is not obvious, for example, to solve this programming challenge, we first need to check if a number is Armstrong or not, and to do this we need individual digits of the number. how do we do that? well, there is a programming technique, which you might have learned while doing number palindrome exercise.

Top 16 Java ArrayList Tutorials and Examples for Beginners - Best of Lot

Most of the Java interview questions on ArrayList asked to freshers or Java developers with 1 to 2 years experience is just simply how to do task e.g. how to sort arraylist, how to serach element, how to remove an element using iterator etc. Since, I have written lots of Java tutorials on ArrayList, covering many general purpose tasks e.g. how to create an object of ArrayList and initialize to how to sort ArrayList in ascending and descending order etc. On request of my readers, I am creating this mega list of ArrayList tutorials, which will help you to learn everything about ArrayList class. These tutorials are great for beginners and even experienced Java developers can learn a trick or two.

String vs StringBuffer vs StringBuilder in Java? Example

Difference between String, StringBuffer, and StringBuilder
The String is one of the most important classes in Java and anyone who starts with Java programming uses String to print something on the console by using famous System.out.println() statements. Many Java beginners are not aware that String is immutable and final in Java and every modification in String creates a new String object. For example, when you get the substring, you get a new String, when you convert uppercase String to lowercase, a new String is created. Even when you remove space by calling the trim() method, a new String is returned. 

Strategy Design Pattern and Open Closed Principle in Java - Example

Strategy design pattern is based upon open closed design principle, the 'O' of famous SOLID design principles. It's one of the popular pattern in the field of object-oriented analysis and design along with Decorator, Observer and Factory patterns. Strategy pattern allows you to encapsulate possible changes in a process and encapsulate that in a Strategy class. By doing that your process (mainly a method) depends upon a strategy, higher level of abstraction than implementation. This makes your process open for extension by providing new Strategy implementation, but closed for modification, because the introduction of a new strategy doesn't require a change in a tested method. That's how it confirms open closed design principle.

OCAJP 8 FAQ - Oracle Certified Associate Java Programmer I Certification (1Z0–808) Frequently asked Questions

The Oracle Certifications is one of the most repeated, industry-recognized certifications. It also provides Java certifications like Oracle Certified Associate Java Programmer, also known as OCAJP and Oracle Certified Professional Java Programmer, also known as OCPJP. These two are most popular Java certification and there are many benefits of passing them e.g. better chance to get a Java development job, improved performance on Java interviews, better salary rise, and promotions, and better opportunity for moving abroad.

SubQuery Example in SQL – Correlated vs Noncorrelated

SubQuery in SQL is a query inside another query. Some time to get particular information from a database you may need to fire two separate SQL queries, subQuery is a way to combine or join them in a single query. SQL query which is on the inner part of the main query is called inner query while the outer part of the main query is called outer query. for example in below SQL query

SELECT name FROM City WHERE pincode IN (SELECT pincode FROM pin WHERE zone='west')

section not highlighted is OUTER query while section highlighted with grey is INNER query.

java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver [Solution]

This error comes when you try to connect to the Microsoft SQL Server database from Java program but the required JDBC driver is not available in Classpath or driver is available in CLASSPATH but the class loader is not able to find it due to classpath intricacies. Depending upon your situation, a solution could be as simple as downloading any of sqljdbc.jar, sqljdbc4.jar or sqljdbc41.jar, based upon the Java version you are using and adding them into CLASSPATH as set CLASSPATH = %CLASSPATH%; (path to Microsoft JDBC driver) in Windows. BTW, in most of the cases "java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver" comes because of classpath intricacies.

How to Convert Fahrenheit to Celsius in Java with Example

In this Java tutorial, you will learn how to write a program to convert Fahrenheit to Celsius in Java. Fahrenheit is a thermodynamic temperature scale, where the freezing point of water is 32 degrees Fahrenheit (°F) and the boiling point of water is 212°F (at standard atmospheric pressure). This puts the boiling and freezing points of water exactly 180 degrees apart. Therefore, a degree on the Fahrenheit scale is 1/180 of the interval between the freezing point and the boiling point of water. Absolute zero is defined as -459.67°F. If you know, in the Celsius scale, the freezing point of water is at 0ºC and the boiling point of water is at 100ºC. By using these facts, you can easily deduce a formula to convert Fahrenheit temperature into Celsius.

Top 30 Linked List Algorithm Questions from Programming/Coding Interviews

The linked list is one of the most common and essential data structure and that's why you would frequently find linked list based coding questions on interviews. The range of questions can be from simple questions like finding the length of a linked list to very difficult e.g. merging two sorted linked lists. Nevertheless, the point is that you should be familiar with linked list data structure and must know how to perform basics task in the linked list e.g. adding or removing nodes from a linked list, traversing order linked list and implementing linked list in your choice of programming language e.g. Java, C++, C, or Python.

How to use wait, notify and notifyAll in Java - Producer Consumer Example

You can use wait, notify, and notifyAll methods to communicate between threads in Java. For example, if you have two threads running in your program e.g.Producer and Consumer then producer thread can communicate to the consumer that it can start consuming now because there are items to consume in the queue. Similarly, a consumer thread can tell the producer that it can also start putting items now because there is some space in the queue, which is created as a result of consumption. A thread can use the wait() method to pause and do nothing depending upon some condition. For example, in the producer-consumer problem, producer thread should wait if the queue is full and consumer thread should wait if the queue is empty.