It's all about Java

 Java Classes and Objects: Classes and objects both are treated in similar way in all programming languages. Java is not exception. Understanding classes and objects with real world example Consider a physical class room with lot of real world objects. What we Observe in class room..? Chairs  Table  Students  Teacher  Black board Markers and Erasers etc So, a programmer needs to instruct the computer, how to create a class room object and it's subsequent objects. like, chair, table, teacher and student etc. If programmer wants to create or develop a School application, he would need to create: class room object Office room object, Student object, Stationary object Play room object etc Let us now create School application with above mentioned objects and classes using java programming language. To create Objects, first of all, we have to create respective classes in java public class School_Application{      public Student students;     ...

 Write code or write code in right way... Writing a coding solution to a problem can be done in many ways. If the solution can be obtained with less number of code lines, then it is easy to understand and maintain. But what if code is large with having millions of lines. Moreover maintenance and readability becomes difficult as the code base grows... Right?  In this blog I want to share my views and experiences on writing code efficiently and effectively with less maintenance efforts. Aspects to consider while coding: Naming convention Cyclomatic Complexity SOLID principles DRY Principle Managing dead code Comments Naming conventions: Every programming language mandates few norms in order to name variables, classes and functions etc. For ex: Java uses class names first letter to be a alphabet and rest to be lower case letters.  But if we dig little bit more, naming conventions are not limited to only upper case or lower case letters and using alphanumeric letters etc. Nam...

Consider Below points before choosing List concrete implementations for your use case:  ArrayList is a linear data structure and  re-sizable/dynamic array   Initial size can be given. and if not given the default size is 10   It is always good practice to give initial size and advised not to give very large number as size   Good programmers prefer ArrayList to LinkedList if retrieval operations is done more frequently than insertion and deletions of elements.   Better choose LinkedList if insertion and deletion operations are done frequently compared to retrieval operations.   Lists are not sorted. if required use Collections.sort() to sort   Collections.sort() uses optimized merge sort [tim sort] on ArrayList   However legacy merge sort also can be used using a switch. But it is going to be deprecated  in near future  The major difference between ArrayList and LinkedList is RandomAccess behavior...

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...

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...

Exception: Exception in a programming language and in English language is pretty similar. Exception means being different from or not following the rules. And in programming language like Java, exception is  an event which occurs during the execution of a program that disturbs the complete flow of application or program. When something beyond expected happens while executing a program is considered as an error. handling these errors or abnormality is called as Exception handling. Exception Handling: Exception handling in java is managed with the help of java keywords and java API support..              1. Java Keywords             2. Java API support Java Keywords:   There are 5 keywords in Java.           1. Try           2. catch           3. finally           4. throw    and 5. throws These five keywor...

Java is an object oriented programming language which can be downloaded and installed in your local Machine from java.com To explain java binaries and tools requires block diagram which gives clear picture. For now I brief few important tools. JDK - java development toolkit JVM - Java virtual machine JRE - Java Run time environment From oracle site we can download JDK which is shipped along with JVM and JRM. Mostly java programmers need the JDK. For end users JRE alone is enough. Basic OOPS characteristics are Inheritance Encapsulation Abstraction and Polymorphism The above concepts collectively makes application software extendable and changeable with less effort. Also helps in Developing design patterns. Design patterns gives solutions for common challenges usually a programmer faces while development applications. Factory design pattern, Abstract design pattern, Builder pattern etc. I explain these Design patterns in another article. Inheritance : Inherita...

Immutable objects and mutable objects with an example  In object oriented programming language, in short OOPS, every problem, precisely every requirement is viewed as an object. Understanding the problem in this point of view brings many good things possible in programming like encapsulation, abstraction, polymorphism and inheritance. Anyways this post is not intended for describing benefits of OOPS. Object could be any thing. Let us take Car  for an instance. Basically car is an object and it has name, wheels, metal body, engine, maximum speed,  gear box etc as properties. Let us consider the car name is Ferrari, maximum speed is 200 km per hr with 6 gears. While driving the car driver can change the speed of the car and change the gear etc. So while car is running it's current speed, current gear are considered to be state of the object. The current speed can be changed using accelerator and gear can be changed using gear box. These can be considered as ...

This article is continuation of previous post JFrame usage demo . Please read it before continuing. This post uses the same example code shown in  JFrame usage demo  with JLabel changes and introduces layout manager BorderLayout. Layout Manager: Layout manager is responsible to arrange components on containers. Usually every swing container is created with a default layout manager but can be changed with setLayout() api. For example JFrame uses BorderLayout as default layout amanger. Java program for JLabel 1  2   import java.awt.BorderLayout; 3   import java.awt.Color; 4   import java.awt.Font; 5  6   import javax.swing.JFrame; 7   import javax.swing.JLabel; 8   import javax.swing.SwingUtilities; 9  10  /** 11   * 12   * Simple class to demonstrate JLabel of swing toolkit 13   * 14   * @author Nagasharath 15   * 16  ...

This post helps in understanding usage of JFrame class with an example Swing toolkit categorizes components into 2 types. They are: Containers Controls Containers allows Controls to be arranged on them. JPanel, JFrame and JDialog are few which are frequently used. Controls are components like Buttons, labels, tables etc. These controls are arranged on containers using different layout managers. All Swing class names starts with J stands for J ava which symbolizes swing is pure java!   Layout Managers: Layout manager is responsible for laying out controls on containers according to the business requirement. Example layout managers are BorderLayout, GridLayout, GridBagLayout and FlowLayout. Few points about JFrame: JFrame is considered as a main window of the application.for almost all swing based applications All other controls and containers are created as child components of JFrame JFrama holds special components like  Menu bar, Tool bar etc...

Java Multi threaded programming basics with Reentrant locks As we have seen in earlier post that implicit locking mechanism achieved using synchronized keyword slows down the application performance. Hence java concurrency api gives explicit locking mechanism to achieve mutual exclusion among shared object. How using explicit locks are better than implicit lock? Explicit lock acquires lock per Thread basis and not per method invoke basis. It is inverse in the case of implicit lock.   If a method is synchronized then every invocation of that method involves acquiring and releasing of lock. This process really slows down the application performance.  Hence it is always good idea to prefer reentrent lock or explicit lock to implicit lock. ReentrantLock is a class available in java.util.concurrency package lock() and unlock() methods are used used to acquire and release the lock. Condition class is used in place of Object class wait(), notifyAll() and notify(). ...

Graphical user interface in short GUI makes computer users easy to understand and use the application software comfortably. Almost all modern programming languages allows application developers to develop GUIs. Java has AWT/Swing as default API as part of Java Foundation classes in short JFC which are shipped with JDK. Hence these toolkits can be used directly in our applications with out adding external libraries like jars to our application's class path. But there are some other toolkits which found useful and industry endorsed in developing GUI.      SWT       JFaces [Framework for SWT]      Java FX      Swing      AWT AWT: Abstract window toolkit is available since java first version. AWT uses native operating system resources like Fonts, colors and components like table, tree, dialogues, windows etc. Few notable points about AWT: AWT is heavy weight. It uses OS resources There are l...

Every Java programmer must read and understand the following books. 1. Effective Java 2. Concurrency in practice Effective Java: This book is authored by Joshua Bloch. He took the major role in authoring the java.util package which is [collection framework] one of the java core libraries. He explains the best practices that every programmer should consider while writing java programs. Some of them are: Contract between hashcode() and equals() of Object class when programmer overrides one of these methods in their classes Exceptions concurrency: Inter thread communication, synchronization etc Immutable Objects The above points are few among others. Concurrency in practice: This book gives complete explanation about how efficient concurrency is achieved in java programs using concurrency utility classes which were introduced in Java 5 version. This book is authored by: Brian Goetz Tim peierls Joshua Bloch Joseph Bowbeer David Holmes and Doug Lea ...

Simple program which demonstrates Swing/AWT Grid layout: This post is intended to the beginners of swing/awt. This below program creates a JFrame with 2 labels, 2 textfields and 2 buttons. import java.awt.GridLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPasswordField; import javax.swing.JTextField; /**  * @author Nagasharath Kopalle  *  * Simple program to demontrate Gridlayout  *  */ public class GridLayoutDemo extends JFrame { private JLabel labelName = null; private JTextField textFieldName = null; private JLabel labelPassword = null; private JPasswordField passwordFieldPassword = null; private JButton buttonSubmit = null; private JButton buttonCancel = null; /** * */ public GridLayoutDemo() { initComponents(); } /** * instantiates components and adds properties. */ void initComponents() { this.setTitle("Grid Layout Dem...

Eclipse Oxygen Java editor Shortcuts helps in editing source code more comfortably. Frequently used default shortcuts are listed below.  Description Shortcut Delete Line CTRL + D Copy Line CTRL + ALT + Down Arrow Add method level, class level, member level Comments SHIFT + ALT + J Format Java Source code CTRL + SHIFT + F Make line commented CTRL + / Make multiple lines [block] commented   CTRL + SHIFT + / Search selected similar word within the source document CTRL + K Select line from beginning to end SHIFT + End key Select line from end to beginning SHIFT + Home key Select Word by word in same line CTRL + SHIFT + Right Arrow Move line above ALT + Up Arrow Move line below ALT + Down Arrow Shortcuts can ...