How to Increase the Heap Size in Your Netbeans or Servers

Hi!

Here is the solution for your heap size trouble, here i have post this solution because i have facing this trouble for a while am doing project in netbeans,so i made decision to post this solution in my blog.

You can set JVM parameters when you start Tomcat from NetBeans as follows:
1. Open the Services window and expand Servers
2. Right-click the Tomcat server and select Properties to open the Servers
dialog
2. Click the Platform tab and set the VM options

You can set the JVM parameters when you start Tomcat outside NetBeans as
follows:
1. Go the the Tomcat installation folder's bin directory and edit
startup.bat
2. Add the following line (replacing 256 with whatever value you want)
set JAVA_OPTS= -Xms256M -Xmx512M
before
call "%EXECUTABLE%" start %CMD_LINE_ARGS% 






For Further Clarification just refer this website


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How Will Java Technology Change My Life?

We can't promise you fame, fortune, or even a job if you learn the Java programming language. Still, it is likely to make your programs better and requires less effort than other languages. We believe that Java technology will help you do the following:

Get started quickly: Although the Java programming language is a powerful object-oriented language, it's easy to learn, especially for programmers already familiar with C or C++.

Write less code: Comparisons of program metrics (class counts, method counts, and so on) suggest that a program written in the Java programming language can be four times smaller than the same program written in C++.

Write better code: The Java programming language encourages good coding practices, and automatic garbage collection helps you avoid memory leaks. Its object orientation, its JavaBeans^TM component architecture, and its wide-ranging, easily extendible API let you reuse existing, tested code and introduce fewer bugs.

Develop programs more quickly: The Java programming language is simpler than C++, and as such, your development time could be up to twice as fast when writing in it. Your programs will also require fewer lines of code.

Avoid platform dependencies: You can keep your program portable by avoiding the use of libraries written in other languages.

Write once, run anywhere: Because applications written in the Java programming language are compiled into machine-independent bytecodes, they run consistently on any Java platform.

Distribute software more easily: With Java Web Start software, users will be able to launch your applications with a single click of the mouse. An automatic version check at startup ensures that users are always up to date with the latest version of your software. If an update is available, the Java Web Start software will automatically update their installation.

ITS ALL ABOUT JAVA!

JAVA TECHNOLOGY:

Java technology is both a programming language and a platform.

JAVA PROGRAMMING LANGUAGE:

The Java programming language is a high-level language that can be characterized by all of the following buzzwords:

Simple, Object Oriented ,Distributed,Multithreaded,Dynamic,Architectural neutral,Portable,
Highperformance,Robust,Secure.

In the Java programming language, all source code is first written in plain text files ending with the .java extension. Those source files are then compiled into .class files by the javac compiler. A .class file does not contain code that is native to your processor; it instead contains bytecodes — the machine language of the Java Virtual Machine

the java launcher tool then runs your application with an instance of the Java Virtual Machine.
JAVA PLATFORM:

A platform is the hardware or software environment in which a program runs. We've already mentioned some of the most popular platforms like Microsoft Windows, Linux, Solaris OS, and Mac OS. Most platforms can be described as a combination of the operating system and underlying hardware. The Java platform differs from most other platforms in that it's a software-only platform that runs on top of other hardware-based platforms.

The Java platform has two components:

• The Java Virtual Machine
• The Java Application Programming Interface (API)

The API is a large collection of ready-made software components that provide many useful capabilities. It is grouped into libraries of related classes and interfaces; these libraries are known as packages.

As a platform-independent environment, the Java platform can be a bit slower than native code. However, advances in compiler and virtual machine technologies are bringing performance close to that of native code without threatening portability.

What Can Java Technology Do?

The general-purpose, high-level Java programming language is a powerful software platform. Every full implementation of the Java platform gives you the following features:

Development Tools: The development tools provide everything you'll need for compiling, running, monitoring, debugging, and documenting your applications. As a new developer, the main tools you'll be using are the javac compiler, the java launcher, and the javadoc documentation tool.

Application Programming Interface (API): The API provides the core functionality of the Java programming language. It offers a wide array of useful classes ready for use in your own applications. It spans everything from basic objects, to networking and security, to XML generation and database access, and more. The core API is very large;

Deployment Technologies: The JDK software provides standard mechanisms such as the Java Web Start software and Java Plug-In software for deploying your applications to end users.

User Interface Toolkits: The Swing and Java 2D toolkits make it possible to create sophisticated Graphical User Interfaces (GUIs).

Integration Libraries: Integration libraries such as the Java IDL API, JDBC^TM API, Java Naming and Directory Interface ("J.N.D.I.") API, Java RMI, and Java Remote Method Invocation over Internet Inter-ORB Protocol Technology (Java RMI-IIOP Technology) enable database access and manipulation of remote objects.

What is Java!!!!!

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of computer architecture.

The original and reference implementation Java compilers, virtual machines, and class libraries were developed by Sun from 1995. As of May 2007, in compliance with the specifications of the Java Community Process, Sun made available most of their Java technologies as free software under the GNU General Public License. Others have also developed alternative implementations of these Sun technologies, such as the GNU Compiler for Java and GNU Classpath.



James Gosling initiated the Java language project in June 1991 for use in one of his many set-top box projects.[5] The language, initially called Oak after an oak tree that stood outside Gosling's office, also went by the name Green and ended up later renamed as Java, from a list of random words.[6] Gosling aimed to implement a virtual machine and a language that had a familiar C/C++ style of notation.[7]

Sun released the first public implementation as Java 1.0 in 1995. It promised "Write Once, Run Anywhere" (WORA), providing no-cost run-times on popular platforms. Fairly secure and featuring configurable security, it allowed network- and file-access restrictions. Major web browsers soon incorporated the ability to run Java applets within web pages, and Java quickly became popular. With the advent of Java 2 (released initially as J2SE 1.2 in December 1998), new versions had multiple configurations built for different types of platforms. For example, J2EE targeted enterprise applications and the greatly stripped-down version J2ME for mobile applications. J2SE designated the Standard Edition. In 2006, for marketing purposes, Sun renamed new J2 versions as Java EE, Java ME, and Java SE, respectively.

In 1997, Sun Microsystems approached the ISO/IEC JTC1 standards body and later the Ecma International to formalize Java, but it soon withdrew from the process.[8] Java remains a de facto standard, controlled through the Java Community Process.[9] At one time, Sun made most of its Java implementations available without charge, despite their proprietary software status. Sun generated revenue from Java through the selling of licenses for specialized products such as the Java Enterprise System. Sun distinguishes between its Software Development Kit (SDK) and Runtime Environment (JRE) (a subset of the SDK); the primary distinction involves the JRE's lack of the compiler, utility programs, and header files.

On 13 November 2006, Sun released much of Java as free and open source software under the terms of the GNU General Public License (GPL). On 8 May 2007 Sun finished the process, making all of Java's core code free and open-source, aside from a small portion of code to which Sun did not hold the copyright.[10]


Primary goals

There were five primary goals in the creation of the Java language:[11]

1. It should be "simple, object oriented, and familiar".
2. It should be "robust and secure".
3. It should be "architecture neutral and portable".
4. It should execute with "high performance".
5. It should be "interpreted, threaded, and dynamic".


Syntax

The syntax of Java is largely derived from C++. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object oriented language. All code is written inside a class and everything is an object, with the exception of the intrinsic data types (ordinal and real numbers, boolean values, and characters), which are not classes for performance reasons.

Java suppresses several features (such as operator overloading and multiple inheritance) for classes in order to simplify the language and to prevent possible errors and anti-pattern design.


Example:

public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}


Brief Explanation about this program:


By convention, source files are named after the public class they contain, appending the suffix .java, for example, HelloWorld.java. It must first be compiled into bytecode, using a Java compiler, producing a file named HelloWorld.class. Only then can it be executed, or 'launched'. The java source file may only contain one public class but can contain multiple classes with less than public access and any number of public inner classes.

A class that is declared private may be stored in any .java file. The compiler will generate a class file for each class defined in the source file. The name of the class file is the name of the class, with .class appended. For class file generation, anonymous classes are treated as if their name was the concatenation of the name of their enclosing class, a $, and an integer.

The keyword public denotes that a method can be called from code in other classes, or that a class may be used by classes outside the class hierarchy. The class hierarchy is related to the name of the directory in which the.java file is.

The keyword static in front of a method indicates a static method, which is associated only with the class and not with any specific instance of that class. Only static methods can be invoked without a reference to an object. Static methods cannot access any method variables that are not static.

The keyword void indicates that the main method does not return any value to the caller. If a Java program is to exit with an error code, it must call System.exit()

The method name "main" is not a keyword in the Java language. It is simply the name of the method the Java launcher calls to pass control to the program. Java classes that run in managed environments such as applets and Enterprise Java Beans do not use or need a main() method. A java program may contain multiple classes that have main methods, which means that the VM needs to be explicitly told which class to launch from.

The main method must accept an array of String objects. By convention, it is referenced as args although any other legal identifier name can be used. Since Java 5, the main method can also use variable arguments, in the form of public static void main(String... args), allowing the main method to be invoked with an arbitrary number of String arguments. The effect of this alternate declaration is semantically identical (the args parameter is still an array of String objects), but allows an alternate syntax for creating and passing the array.

The Java launcher launches Java by loading a given class (specified on the command line or as an attribute in a JAR) and starting its public static void main(String[]) method. Stand-alone programs must declare this method explicitly. The String[] args parameter is an array of String objects containing any arguments passed to the class. The parameters to main are often passed by means of a command line.

Printing is part of a Java standard library: The System class defines a public static field called out. The out object is an instance of the PrintStream class and provides many methods for printing data to standard out, including println(String) which also appends a new line to the passed string.

CLOSE LOOK ON JAVA MAIL!!

The layout of packages and classes in the Java Mail API demonstrates one of the primary goals of its designers -- that the level of effort required by the developer to build an application should be dictated by the complexity of the application and the level of control required by the developer for the application. In other words, keep the API as simple as possible. The example application included in this article and the examples that ship with the Java Mail API amply demonstrate this point.

On first glance, the number of Java Mail API classes and the detailed layout of these classes may cause you to believe you're in for a heavy learning curve. But in reality, once you get working, you'll find that this API is a simple and handy tool for implementing robust mail/messaging functionality in your applications.

Analysis of the primary Java Mail API package classes provides insight into the common mechanics of e-mail messaging systems. A high-level overview of the classes in the relative order in which they are normally encountered in a typical application reveals the simplicity of the Java Mail API.


Although the Java Mail API contains many more classes than those discussed here, concentrating on some of the core classes to start with makes it easy to understand the essence of the API. The following is a detailed description of these core classes, which include javax.mail.Session, javax.mail.Store, javax.mail.Transport, javax.mail.Folder, and javax.mail.Message.

javax.mail.Session

The javax.mail.Session class is the top-level entry class for the Java Mail API, and its most commonly used methods provide the ability to control and load the classes that represent the service provider implementations (SPI) for various mail protocols. For example, instances of the javax.mail.Store and javax.mail.Session classes -- described below -- are obtained via the Session class. (Note: A service provider is a developer and/or vendor that provides an implementation for an API; examples of Java Mail API implementations include POP3, SMTP, and IMAP4 -


javax.mail.Store

The javax.mail.Store class is implemented by a service provider, such as a POP Mail implementation developer, and allows for read, write, monitor, and search access for a particular mail protocol. The javax.mail.Folder class is accessed through this class and is detailed below.

javax.mail.Transport

The javax.mail.Transport class is another provider-implemented class and is used for sending a message over a specific protocol.

javax.mail.Folder

The javax.mail.Folder class is implemented by a provider; it gives hierarchical organization to mail messages and provides access to e-mail messages in the form of javax.mail.Message class objects.

javax.mail.Message

The javax.mail.Message class is implemented by a provider and models all the details of an actual e-mail message, such as the subject line, sender/recipient e-mail address, sent date, and so on. The guidelines for providers who implement the javax.mail.Message dictate that the actual fetching of e-mail message components should be delayed as long as possible in order to make this class as lightweight as possible.

The Java Mail API and JAF

One design fact worth mentioning is that the Java Mail API is tied to, or rather leverages, another Java extension: the Java Activation Framework (JAF). The JAF is intended to unify the manner of working with the multitude of data formats that are available, whether they be simple text or extremely complex documents composed of images, audio, video, and even "live" objects. In this sense, it might be useful to think of the JAF as providing for Java what plug-ins provide to a Web browser.

A sample Java Mail application

A "list server application" serves as the focal point for a distributed group discussion system based on e-mail. As such, it is a very common and useful way for subscribers to discuss common-interest subjects.

The following Java Mail API-based application is a working example of a useful middletier list server application. The Java Mail API makes this application easy to create (using the default POP3 and SMTP implementations) and ensures that it will easily support any provider-implemented systems that should arise. For example, the current application easily supports POP3, SMTP, and IMAP servers

// create some properties and get the default Session
//
Properties props = new Properties();
props.put("mail.smtp.host", _smtpHost);
Session session = Session.getDefaultInstance(props, null);

// Send newMessage
//
Transport transport = session.getTransport(SMTP_MAIL);
transport.connect(_smtpHost, _user, _password);
transport.sendMessage(newMessage, _toList);



The code for setting up the message fields such as to, from, subject, and date is very simple:



// create a message
//
Address replyToList[] = { new InternetAddress(replyTo) };
Message newMessage = new MimeMessage(session);
if (_fromName != null)
newMessage.setFrom(new InternetAddress(from,
_fromName + " on behalf of " + replyTo));
else
newMessage.setFrom(new InternetAddress(from));
newMessage.setReplyTo(replyToList);
newMessage.setRecipients(Message.RecipientType.BCC, _toList);
newMessage.setSubject(subject);
newMessage.setSentDate(sentDate);


Setting the contents of the message requires reading in the desired contents and then calling the appropriate setContents...() routine as follows:

// Set message contents
//
Object content = message.getContent();
String debugText = "Subject: " + subject + ", Sent date: " + sentDate;
if (content instanceof Multipart)
{
debugMsg("Sending Multipart message (" + debugText + ")");
newMessage.setContent((Multipart)message.getContent());
}
else
{
debugMsg("Sending Text message (" + debugText + ")");
newMessage.setText((String)content);
}

INTRODUCING THE JAVA MAIL !

The JavaMail API is an optional package (standard extension) for reading, composing, and sending electronic messages. You use the package to create Mail User Agent (MUA) type programs, similar to Eudora, Pine, and Microsoft Outlook. Its main purpose is not for transporting, delivering, and forwarding messages like sendmail or other Mail Transfer Agent

(MTA) type programs. In other words, users interact with MUA-type programs to read and write emails. MUAs rely on MTAs to handle the actual delivery.

The JavaMail API is designed to provide protocol-independent access for sending and receiving messages by dividing the API into two parts:

• The first part of the API is the focus of this course. Basically, how to send and receive messages independent of the provider/protocol.
• The second part speaks the protocol-specific languages, like SMTP, POP, IMAP, and NNTP. With the JavaMail API, in order to communicate with a server, you need a provider for a protocol. The creation of protocol-specific providers is not covered in this course as Sun provides a sufficient set for free.

Reviewing Protocols

Before looking into the JavaMail API specifics, step back and take a look at the protocols used with the API. There are basically four that you'll come to know and love:

• SMTP
• POP
• IMAP
• MIME

You will also run across NNTP and some others. Understanding the basics of all the protocols will help you understand how to use the JavaMail API. While the API is designed to be protocol agnostic, you can't overcome the limitations of the underlying protocols. If a capability isn't supported by a chosen protocol, the JavaMail API doesn't magically add the capability on top of it. (As you'll soon see, this usually is a problem when working with POP.)

SMTP

The Simple Mail Transfer Protocol (SMTP) is the mechanism for delivery of email. In the context of the JavaMail API, your JavaMail-based program will communicate with your company or Internet Service Provider's (ISP's) SMTP server. That SMTP server will relay the message on to the SMTP server of the recipient(s) to eventually be acquired by the user(s) through POP or IMAP. This does not require your SMTP server to be an open relay, as authentication is supported, but it is your responsibility to ensure the SMTP server is configured properly. There is nothing in the JavaMail API for tasks like configuring a server to relay messages or to add and remove email accounts.

POP

POP stands for Post Office Protocol. Currently in version 3, also known as POP3, RFC 1939 this protocol. POP is the mechanism most people on the Internet use to get their mail. It defines support for a single mailbox for each user. That is all it does, and that is also the source of most confusion. Much of what people are familiar with when using POP, like the ability to see how many new mail messages they have, are not supported by POP at all. These capabilities are built into programs like Eudora or Microsoft Outlook, which remember things like the last mail received and calculate how many are new for you. So, when using the JavaMail API, if you want this type of information, you have to calculate it yourself.

IMAP

IMAP is a more advanced protocol for receiving messages. Defined in RFC 2060, IMAP stands for Internet Message Access Protocol, and is currently in version 4, also known as IMAP4. When using IMAP, your mail server must support the protocol. You can't just change your program to use IMAP instead of POP and expect everything in IMAP to be supported. Assuming your mail server supports IMAP, your JavaMail-based program can take advantage of users having multiple folders on the server and these folders can be shared by multiple users.

Due to the more advanced capabilities, you might think IMAP would be used by everyone. It isn't. It places a much heavier burden on the mail server, requiring the server to receive the new messages, deliver them to users when requested, and maintain them in multiple folders for each user. While this does centralize backups, as users' long-term mail folders get larger and larger, everyone suffers when disk space is exhausted. With POP, saved messages get offloaded from the mail server.

MIME

MIME stands for Multipurpose Internet Mail Extensions. It is not a mail transfer protocol. Instead, it defines the content of what is transferred: the format of the messages, attachments, and so on. There are many different documents that take effect here: RFC 822,RFC 2045, RFC 2046 , and RFC 2047. As a user of the JavaMail API, you usually don't need to worry about these formats. However, these formats do exist and are used by your programs.

NNTP and Others

Because of the split of the JavaMail API between provider and everything else, you can easily add support for additional protocols. Sun maintains a list of third-party provider that take advantage of protocols that Sun doesn't provide support for, out-of-the-box. There, you'll find support for NNTP (Network News Transport Protocol) [newsgroups], S/MIME (Secure Multipurpose Internet Mail Extensions), and more.