It's all about Java

File Management in OS File management includes files and folders creation, copy and paste operations, reading the file and writing into files and deleting the files and folders  And also reading meta data about files and folders. It may include file free space, occupied space and read/write permissions etc. These above operations are considered as file management and managed by respective operating system. GUI that represents Windows File Manager File Management with Java  Though Java is platform independent, programming language depends on native file IO resources of operating system. This is possible with the Java API support. These API are categorized into 2 types. Readers and Writers: Readers and writers does the IO operations, character by character InputStream and OutputStream: Where as InputStream and OutputStream does IO operations byte by byte Below are simple Java programs that demonstrates different File IO operations. Program for creating directory package com.all...

NullPointerException causes and reasons Since Java is object oriented programming language, every thing is considered to be an object. and there is always a scope of an object to be null or "No value".  Since Java supports primitive data types, Java is not considered to be pure Java object oriented programming language.   Few Notable points about NullPointerException NullPointerExceptions is unchecked exception Please read post  Exception handling and java keywords before reading this article Usually if program tries to fetch the value from reference and finds nothing as value, then program throws NullPointerException 'Zero' is not null And empty String is not considered to be null It is not the subclass of RuntimeException class Demo code that throws NullPointerException  package com.allabtjava.blog; public class DemoNullPointerException { class BeanDemo { String name; Integer ID; public String getName() { return name; } public void s...

Evolution of Java: First of all, The Java programming language and it's tools that we currenly using is not what actually expected. This language started as a project to give solutions for embedded devices, mobile phones and other portable peripherals.  Initially, the Java was called Oak.  Why it is Oak first..? and Why it transformed to Java..? The team of five technocrats including Dr. James Gosling and also known as Dr. Java, together working on a project, which expected to give solutions on embedded devices, portable smart devices and TV Set top Boxes etc. at Sun Micro Systems.  In the process of achieving this solution, at their breaktime, team used to relax with a coffee by having a glimpse on a scenery of Oak tree next to their facility.  Once the project has come to conclusion and in the process of giving a title to it, they noticed the Oak trees [Always observing them in their break time], they named this programming language as Oak. Oak Logo Why it transfor...

IDE: Integrated Development Environment Integrated development environment, in short IDE is a convenient environment to write, execute and  debug the code or programs on a single platform. IDEs support not only writing code smoothly but also provides a provision to write scripts, XML files, simple text files and build scripts like Ant, Maven are few among others. In short IDEs are development environments to execute complete development activities using one application. IDEs and Editors IDEs and Editors fulfills the same purpose. That is writing code. But IDEs are glued or closely works with respective programming language's compilers, runtime environments, profilers and other language specific tools to put developer in a comfortable zone.  Some of the features of IDE: Auto completion Syntax Highlighting Code debugger Profilers Multipage editors Auto completion: Auto completion feature suggests APIs [methods, classes and interfaces] and keywords etc as we start typing in the e...

Software development activities can be managed and taken care with different life cycle models. These life cycle models has became legacy since few years. Few of the available Software Development Life Cycle Models in short SDLC are Win-Win Model and Waterfall Model etc. These traditional models has different phases of development.           1. Requirements            2. Analysis            3. Design            4. Implementation            5. Test           6. Documentation  and 7. Maintenance  In SDLC, the above stages are freezed one after the other. If developer is in Design phase and realized that there could be a possibility of change in requirements, then it is not possible to go back one phase and fix in Requirement phase.  These scenarios and use cases has brough...

First of all, please read below blog post to understand basics of Exception Handling in java. Exception handling and java keywords To continue from there, Basically Java default API has hierarchy of  java classes to support different uses cases of exceptions.  The parent class of all Exceptions and Errors is Throwable . Please check below pictorial representation of  API Hierarchy. Exception: The class Exception and any subclasses that are also not subclasses of RuntimeException are checked exceptions. And all subclasses of RuntimeException and RuntimeException class itself are Unchecked exception . Rest all are Checked exceptions Examples of Unchecked Exceptions:            ArrayIndexOutOfBoundException          NullPointerException Error: An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. Most such errors are abnormal conditions. Examples: T...

Unlike AWT, Java Swing tool kit provides feasibilty to create custom components and containers. To understand Java GUI toolkits more clearly, please read my other articles on Swing and AWT.  In this article I focus more on building custom components. Let us see how to create simple Rounded JButton. The below program demonstrates How rounded JButton can be created and added to a JFrame.   Program: import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.GridLayout; import java.awt.Shape; import java.awt.geom.Ellipse2D; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JTextField; import javax.swing.SwingUtilities; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class RoundedJButton extends JButton { /** *  */ private static final long serialVersionUID = 1L; public RoundedJButton(String title) { super(title); Dimension size = getPreferredSize(); size.w...