Java Programming Tutorials

Java Programming Tutorials And Articles
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Introduction This Code snippet is used to capture Screenshot automatically and save it. The below code performs the function of taking screenshots automatically making use of the class java.awt.Robot .The package java.awt contains all of the classes for creating user interfaces and for...
Earlier in client- server computing, each application had its own client program and it worked as a user interface and need to be installed on each user's personal computer. In web applications we mostly use HTML/XHTML which is mostly supported by all the browsers and web page is displayed to the...
Every class has at least one it's own constructor. Constructor creates a instance for the class. Constructor initiates something related to the class's methods. Constructor is the method which name is same to the class. But there are many difference between the method s and the Constructor.In this...
What is an EJB? An Enterprise JavaBean (EJB) is a reusable, portable J2EE component. EJBs consist of methods that encapsulate business logic. For example, an EJB may have business logic that contains a method to update customer data in a database. A variety of remote and local clients can invoke...
Exception is an abnormal condition that arises in the program during execution. When such a condition arises in the program, an appropriate code is written so that it can be handled. It is very much similar to the error codes returned by a subroutine in the C language. Whatever value the function...
Introduction The code which is expected to generate the exception must be enclosed in the try and catch block. The very basic form of the exception-handling block is as following: try { //code which is expected to generate the exception } catch (<ExceptionTypeClass> object) {...
The finally clause is written with the try-catch statement. It is guarenteed to be executed after a catch block or before the method quits. try { // statements } catch (<exception> obj) { // statements }
You have seen that an exception is thrown either implicitly in the try block and there is a catch block ready to handle it. But, there are methods, which throw the exception, but do not catch it within the method body. In this case the method which is throwing the exception must use a throws clause...
Introduction The 'main()' method in Java is referred to the thread that is running, whenever a Java program runs. It calls the main thread because it is the first thread that starts running when a program begins. Other threads can be spawned from this main thread. The main thread must be the...
Introduction The code bound by the try block need not always throw a single exception. If in a try block multiple and varied exceptions are thrown, then you can place multiple catch blocks for the same try block in order to handle all those exceptions. When an exception is thrown it traverses...
Just like the multiple catch blocks, we can also have multiple try blocks. These try blocks may be written independently or we can nest the try blocks within each other, i.e., keep one try-catch block within another try-block. The program structure for nested try statement is: try { //...
Java defines several built-in classes for exception handling. All these classes are a part of the java.lang package which is automatically imported. That is why, while throwing an exception you did not specifically include any package for exception classes. Apart from the built-in exception...
The exception handling mechanism is a cleaner way to impose check upon the conditions which may lead to errors. But you should not be carried away by it and start using exception handling anywhere and everywhere you want. Exceptions must be carefully planned and implemented. The following cases...
Compiler Problems 1. 'javac' is not recognized as an internal or external command, operable program or batch file If you receive this error, it means that Windows is not able to find the compiler (javac). Here's one way to tell Windows where to find javac. Set the PATH as follows on...
Spring Framework Features Spring is a layered Java/J2EE application framework, based on code published in Expert One-on-One J2EE Design and Development by Rod Johnson (Wrox, 2002). Spring includes: - The most complete lightweight container, providing centralized, automated configuration...
We can create a thread in Java by extending Thread Class. A better way to create a thread in Java is to implement Runnable interface. A thread can be created by extending Java Thread class also. Now the question arises why implementing Runnable interface is a better approach? Answer is, if the...
Struts is a free open-source framework for creating Java web applications. Web applications differ from conventional websites in that web applications can create a dynamic response. Many websites deliver only static pages. A web application can interact with databases and business logic engines...
JSTL is a collection of tags similar to HTML that lets you produce dynamic web pages without needing to learn Java. Why JSTL? JavaServer Pages (JSP) technology makes it easy to embed bits of Java code (or scriptlets) in HTML documents. This solution, however, may not be suitable for all HTML...
Comparing Strings To compare strings function equals() is used. String str1 = "XYZ"; String str2 = "xyz"; boolean result = str1.equals(str2); boolean result2 = str1.equalsIgnoreCase(str2);Output
This article demonstrates how to write a simple Stateful Session Bean. It consists of three POJO's: Remote interface, Bean class and EJB client Prerequisites In order to complete the example application, you should be familiar with the following: *...