This article shows how to convert Java objects to from JSON using Gson. Table of contents: 1. Download Google Gson 2. Gson Basic Usages 3. Java Object 4. Convert Object to JSON using Gson 5. Converts JSON to Java Object using Gson 6. Modify JSON with JsonElement 7. Converts Json Array to List objects 8. […]
Oftentimes, we use SSH to remote access into the server to run a Java program. The problem is, we can’t type anything After the Java program is executed like this : $ java -jar example.jar In addition, when the remote access session is expired or terminated, the executed Java program will be killed. Solution To […]
My monthly PCB income tax is increased much since march 2009, HR told me that Malaysia monthly income tax PCB deduction rate is changed since year 2009. Income tax PCB calculation Here’s the calculation. 1. Find your PCB amount in this Income tax PCB 2009 Chart 2. Calculate your taxable salary – Taxable Salary = […]
In Java, we can use str.getBytes(StandardCharsets.UTF_8) to convert a String into a byte[]. String str = "This is a String"; // default charset, a bit dangerous byte[] output1 = str.getBytes(); // in old days, before java 1.7 byte[] output2 = str.getBytes(Charset.forName("UTF-8")); // the best , java 1.7+ , new class StandardCharsets byte[] output3 = str.getBytes(StandardCharsets.UTF_8); […]
In Java, we can use new String(bytes, StandardCharsets.UTF_8) to convert a byte[] to a String. // string to byte[] byte[] bytes = "hello".getBytes(StandardCharsets.UTF_8); // byte[] to string String s = new String(bytes, StandardCharsets.UTF_8); Table of contents 1. byte[] in text and binary data 2. Convert byte[] to String (text data) 3. Convert byte[] to String […]
In this article, we show you how to use Java Cryptography Extension (JCE) to encrypt or decrypt a text via Data Encryption Standard (DES) mechanism. 1. DES Key Create a DES Key. KeyGenerator keygenerator = KeyGenerator.getInstance("DES"); SecretKey myDesKey = keygenerator.generateKey(); 2. Cipher Info Create a Cipher instance from Cipher class, specify the following information and […]
Often times, you may to use “mvn eclipse:eclipse -Dwtpversion=1.5” command to create a web project for Eclipse IDE, but you may encounter the following error messages. Unsupported WTP version: 1.5. This plugin currently supports only the following versions: 1.0 R7 D:\mkyong>mvn eclipse:eclipse -Dwtpversion=1.5 [INFO] Scanning for projects… [INFO] Searching repository for plugin with prefix: ‘eclipse’. […]
Tomcat by default runs on port number 8080, However there is high chance get a port conflict with others program. Sometime we just need to change the Tomcat port number. Steps of changing the Tomcat Port 1) Locate server.xml in {Tomcat installation folder}\ conf \ 2) Find following similar statement <!– Define a non-SSL HTTP/1.1 […]
In some cases, you may need to generate Ant build file (build.xml) for your project integration purpose. For example, the klockwork code analysis tool is required Ant file to perform the static code analysis processes for java project. Maven Ant plugin Maven comes with a handy Ant plugin to generate Ant build file from Maven […]
According to Apache Maven : Downloading in Maven is triggered by a project declaring a dependency that is not present in the local repository (or for a SNAPSHOT, when the remote repository contains one that is newer). By default, Maven will download from the central repository. In Maven, when you’re declared library does not exist […]
By default, Maven will get project dependencies from Maven Local Repository, if it is not found, Maven will get it from the Maven Central Repository Maven Central Repository URL – https://repo.maven.apache.org/maven2 Maven Central Repository Search – https://search.maven.org/ This is how the Maven central repository search website looks like : History This is how the Maven […]
Believe it or not, Java contains Integer buffer overflow as well. I’m not sure is this the correct word to describe it or not, may be you can suggest some 🙂 OK, please take a look at below program, this program print the number of microseconds in a day. public class JavaLongOverflow { public static […]
Today when i debugging a Java Mail program, i find out one of the checking is about “Part.Attachment” and “Part.Inline” in email message. What is the different between Inline attachment and attachment? Inline Attachment Inline attachment usually is an attachment that we can see direclty within the email message body. For Example, In outlook express, […]
There are many monetary values calculation in the financial or e-commerce application, and there is one question that arises for this – Should we use double or float data type to represent the monetary values? Answer: Always uses java.math.BigDecimal to represent the monetary values. 1. Double or Float? Here is an example of using double […]
In Java, you can use following methods to get time in milliseconds Date class – getTime() method Calendar class – getTimeInMillis() method TimeMilisecond.java package com.mkyong.test; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; public class TimeMilisecond { public static void main(String[] argv) throws ParseException { SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss"); String dateInString = "22-01-2015 […]
In Java, you can use the following ways to measure elapsed time in Java. 1. System.nanoTime() This is the recommended solution to measure elapsed time in Java. ExecutionTime1.java package com.mkyong.time; import java.util.concurrent.TimeUnit; public class ExecutionTime1 { public static void main(String[] args) throws InterruptedException { //start long lStartTime = System.nanoTime(); //task calculation(); //end long lEndTime = […]
Regular expression pattern in Java always is the best method to validate an user’s phone number. Here i provide a regex pattern to determines if the phone number is in correct format, the pattern force starting with 3 digits follow by a “-” and 7 digits at the end. \\d{3}-\\d{7} Explanation \\d = only digit […]
Here i show you four ways to loop a List in Java. Iterator loop For loop For loop (Adcance) While loop package com.mkyong.core; import java.util.Arrays; import java.util.Iterator; import java.util.List; public class ArrayToList { public static void main(String[] argv) { String sArray[] = new String[] { "Array 1", "Array 2", "Array 3" }; // convert array […]
Java example to show you how to convert a Array to a List ArrayToList.java package com.mkyong; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class ArrayToList { public static void main(String[] argv) { String sArray[] = new String[] { "A", "B", "C" }; // convert array to list #1 List<String> list = Arrays.asList(sArray); System.out.println(list); […]
By default, Maven local repository is defaulted to ${user.home}/.m2/repository folder : Unix/Mac OS X – ~/.m2/repository Windows – C:\Users\{your-username}\.m2\repository When we compile a Maven project, Maven will download all the project’s dependency and plugin jars into the Maven local repository, save time for next compilation. 1. Find Maven Local Repository 1.1 If the default .m2 […]
Node This article is using the endTime – startTime method to measure the performance of a loop, it ignores the JVM warm up optimization, the result may not consistent or accurately. A better way is using the OpenJDK JMH framework to do the benchmark testing, because it will take care of the JVM warm up […]
Node This article is using the endTime – startTime method to measure the performance of a loop, it ignores the JVM warm up optimization, the result may not consistent or accurately. A better way is using the OpenJDK JMH framework to do the benchmark testing, because it will take care of the JVM warm up […]
I downloaded FallOut3 game today, however it delivered in ISO image format. The ISO image is an archive file or disk image of an optical disc (CD or DVD). Do you know we can extract ISO image file with winrar? We always use winrar to zip or unzip certain files, but we also can use […]
Often time , i like to know my computer, motherboard or CPU temperature. It’s will be better if some utility tools provide the functionality to show all my processors or CPU temperature ~ Here is the two free tools that i used to check my CPU temperature Core Temp Software Name : Core Temp Website […]
A JDBC example to show you how to connect to a PostgreSQL database with a JDBC driver. Tested with: Java 8 PostgreSQL 11 PostgreSQL JDBC driver 42.2.5 1. Download PostgreSQL JDBC Driver Visit http://jdbc.postgresql.org/download.html to download the latest PostgreSQL JDBC Driver. 2. JDBC Connection 2.1 Make a connection to the PostgreSQL database. JDBCExample.java import java.sql.Connection; […]
In SWT, keyboard event is represent by KeyEvent class. We can use KeyListener to receive and process a KeyEvent. The KeyEvent class has three member fields to provide information about the key that generated by event. 1) character – Display a char value of the pressed key. 2) stateMask – Check whether any other keys […]
Develop SWT application without SWT source code attached in Eclipse IDE will make developers feel depress in SWT. Just imaging when we do not know some SWT classes, then mouse point that class and press F3, nothing come out but a black page saying “no SWT source code found, please attach a source”, how you […]
The Standard Widget Toolkit (SWT) is an open source project. However Eclipse SWT plugin does not bundle with SWT source code. We have to manually download it ~ Here is the steps to download the SWT Source Code 1) Visit the Standard Widget Toolkit (SWT) Official Website http://www.eclipse.org/swt/ 2) Under Stable, select your operating system […]
When i received a new mail from yahoo mail box, my yahoo messenger will voice out a typical “de” voice and display a simple dialog box as “Yahoo! Mail 1 new message(s)” I just want my yahoo messenger to voice up a “You’ve got mail” voice whenever any new mail received. Here i show how […]
MouseListener Mouse event processing is easy to implement, we need to implement MouseListener interface and declare all the interface methods. We can attached the MouseListener to a widget with addMouseListener() method. "widget control".addMouseListener(new MouseListener() { public void mouseDown(MouseEvent e) { System.out.println("Mouse Down."); } public void mouseUp(MouseEvent e) { System.out.println("Mouse Up."); } public void mouseDoubleClick(MouseEvent e) […]
I heard a lot of people talking about “Bind variables” will increase java application performance. Is this really true? i skeptical and make a simple performance test between Bind variables in PreparedStatement class and Non Bind variables in Statement class How do i test it? I will create a simple java class and keep sending […]
What is TabFolder? In SWT, TabFolder is a subclass of a Composite class. The TabFolder can include composite object into a single container through a tabbed index. How to create a TabFolder? Here i create a TabFolder composite, add a sashForm composite into a tab 1 and Group composite into a tab 2. import org.eclipse.swt.SWT; […]
What is SashForm? In SWT, SashForm is similar with Group, however it added one more useful feature, it’s allow user to adjust the control size at runtime environment. The SashForm provide this feature by creating a movable line between child widget (button, label, text…). When user drag the “line” it will expand one widget size […]
What is Group In SWT, Group is a subclass of a Composite class. Group is used to improve application appearance and make whole application look more organized. It will draw a rectangular border around all it’s child widgets. Group widget support five styles (actually it is nothing much different) 1) SWT.SHADOW_IN 2) SWT.SHADOW_OUT 3) SWT.SHADOW_NONE […]
In SWT, button widget consists of five buttons style. 1) Normal Button – SWT.PUSH 2) Arrow Button – SWT.ARROW 3) Toggle Button – SWT.TOGGLE 4) Check Box button – SWT.CHECK 5) Radio Button – SWT.RADIO Here i demonstrate how to create those buttons in SWT import org.eclipse.swt.SWT; import org.eclipse.swt.widgets.Button; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; public class […]
What is Label? The Label is the most common and frequent use widget, it’s display static information such as String or Image, and no user input involve. How to create a Label widget? This code snippet will create a label at position x=100, y=50, width = 300, height = 30, and display “I am Label” […]
When we start learn about SWT GUI programming, we always want to figure out how do we positioning the Text field, Label, button and other widget. In SWT, we can use setLocation() or setLocation() method to specify the size and position of a widget or component. Here is the two methods that SWT use to […]
SWT is stand for Standard Widget Toolkit. I do not want to explain what the benefits of it , please search Google for it. Please access SWT Official Website if you want to know more about it. Here is the simple SWT Hello World program import org.eclipse.swt.SWT; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; import org.eclipse.swt.widgets.Text; public class […]
In order to develop SWT application in Eclipse environment, we have to import SWT library into Eclipse Workspace manually. Here is the steps to import SWT library 1) Right click on Java Project – Click Properties 2) Click Java Build Path –> Libraries –> Add Variable –> Configure Variable 3) Click New –> Type a […]
Problem Content Assist (Ctrl + Space) is not working in my Eclipse IDE version 3.3. I have two Eclipse IDE installed, both in my laptop and personal desktop computer. However my laptop Eclipse 3.3’s content assist feature is working perfectly, but not my personal desktop computer. Every time, when i pressed on the Ctrl + […]
