java

Why float type cast

parveen.gupta.23091987 — Tue, 31 Jan 2012 07:10:53 -0500

in java why float we has to be type cast i.e. float a = (float)2.3; and and if 2.3 is consider as double then why there is a need for that ???

Community Discussion

Text to speech without using TTS

sridharkosna — Thu, 08 Dec 2011 05:48:10 -0500

Hi All,
My requirement is to convert a string value to speech without using TTS (freeTTs). how can i achieve this? can anybody give me some idea. it could be helpful.

Enterprise Java

Dynamic check boxes in java

Fatema Mohsen — Fri, 22 Apr 2011 10:05:11 -0400

I was asking how could i create dynamic check boxes in java on a button press,especially without knowing the bounds of each check box.Then remove all checked boxes on another button press.Here is my manually created check boxes code

cb1=new JCheckBox("Task 1");
cb2=new JCheckBox("Task 2");
cb3=new JCheckBox("Task 3");
cb4=new JCheckBox("Task 4");
cb5=new JCheckBox("Task 5");
cb6=new JCheckBox("Task 6");
addTask= new JButton("Add Task");
removeTask= new JButton("Remove Checked");
addTask.addActionListener(this);
removeTask.addActionListener(this);

Core Java

JavaOne 2011

t3chno — Tue, 19 Apr 2011 03:05:52 -0400

My development team is largely Java based. I am aware of Devoxx and would hope to attend next year, but what are the other conferences that would be useful for my requirements?

Mobile Java

show the selected file and folder in tree structure, with checkbox and the checkbox should be only for root elements not for all

itsanandrhere — Wed, 13 Apr 2011 22:19:33 -0400

Dear all,

By using JFileChoor I am able to select file and folders, Getting JList with File Objects and I am showing it with checkbox. Now my requirement is like I want to show the selected file and folder in tree structure, with checkbox and the checkbox should be only for root elements not for all child elements. Please help me as soon as possible, for me its very urgent.

Like if I selected folders ABC and PQR and file XYZ which containt sub folders and few files
now on UI It should be display

Checkbox1 ABC--
--SubFolders
. --SubFolder
. --Files
--Files
Checkbox2 PQR--

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Core Java

QCon or Javaone ????

lisaantony06 — Thu, 24 Mar 2011 05:04:55 -0400

My company allows me to visit one international work related (I'm Java/JEE Developer/Technical Lead interested in polyglot programming) conference each year. I've visited Javapolis (devox) in the past.
For this year I'm looking for a conference which is less technology but a bit more methodology focussed... possible like Oracle Develop or QCon or Javaone What would you recommend?

Tools and Methods

Is XML Slow? - Benchmarking XML

Vipul Gupta — Tue, 22 Mar 2011 03:55:04 -0400

There is a general tendency to think that representing and processing the data of an entire transaction as an XML document is the root cause of slow performance in high volume systems. However, there is a flaw in this kind of thinking and it mostly has to do with a wrong technology or approach being used by the development team. This article will demonstrate how different technologies compare against each other in processing XML documents of varying structural complexity and size. This should allow development teams to choose the most suitable technologies for their application stack, rather than assuming that the slowness is the result of underlying XML processing and usage.

This article will focus on using the Java programming language to evaluate and demonstrate the performance of different XML processing techniques. However, the same results/benchmarks are observed across different languages (.NET, etc.) and systems. As a part of this study we will also make recommendations on which approach offers the best performance based on the underlying system requirements. The article will specifically demonstrate how various technologies compare against each other in terms of the amount of time needed, in each approach, to process an XML document and convert it into the corresponding Object graph.

Techniques Used for Comparison

We picked the most powerful and the most common techniques that are being used by the development community today. Then we ran a suite of tests (for processing XML documents) using each of these chosen alternatives, for a side-by-side comparison of the time taken in the Deserialization process by these alternatives.

The different alternatives that we considered for this article are:

Native Serialization/Deserialization provided by the Java Programming language: Java provides automatic serialization which requires that the class be marked by implementing the marker interface java.io.Serializable. Java then handles serialization internally for any such objects. The standard encoding method uses a simple translation of the fields into a byte stream. Primitives as well as non-transient, non-static referenced objects are encoded into the stream. Each object that is referenced by the serialized object and not marked as transient must also be serialized; and if any object in the complete graph of non-transient object references is not serializable, then the serialization will fail. The developer can influence this behavior by marking objects as transient, or by redefining the serialization for an object so that some portion of the reference graph is truncated and not serialized.
Java Architecture for XML Bindings (JAXB): JAXB is an APIwith a reference implementation and a set of tools that allows automatic two-way mapping between XML documents and Java objects. With a given Document Type Definition (DTD) or a schema, the JAXB compiler can generate a set of Java classes that allow developers to build applications that can read, manipulate and recreate XML documents without writing any logic to process XML elements. In other words, JAXB allows Java developers to access and process XML data without having to know XML or XML processing in great detail. For example, there is no need to create or use a SAX parser or write callback methods. One of the more useful benefits is that the JAXB XJC compiler generates the corresponding Java mapping objects and processing code, which essentially frees developers from manually writing and debugging conversion code. With the auto generated code, developers can write applications that access XML data through Java interfaces and do not need to worry about the structure of data. It is also important to know that JAXB uses SAX as the underlying parsing mechanism.
JAXB with FastInfoSet Library: A binary format standard for XML from the ITU-T and ISO that reduces the size of text-based XML files (XML infosets) and improves parsing speed. Based on ASN.1 notation, Fast Infoset files can be easily compressed to as little as 20% of their original size. When an external schema is used, they can be compressed to an extraordinary 5% of original size.
JAXB with custom compression: In order to have a meaningful comparison between FastInfoSet and JAXB we added a compression/un-compression stage to the processing of XML documents by JAXB, and named this stage as such.
Deserialization using DOM parser: Since JAXB uses SAX as the underlying parsing mechanism; we thought it logical to include DOM parsing which loads the entire XML in memory for manipulation also as part of this study.

Comparison Report

We executed 100,000 iterations* of deserializing a set of XML files having varying sizes, from very small to large, across all the selected technologies and observed the following results. The goal was to transmit the same atomic piece of information (e.g. a message) in various different formats: XML, binary, etc. What is important is that semantically we are transmitting the exact same information with no loss due to compression. The figure below shows the results of the tests conducted by us.

*(100,000 iterations resulted in convergence of numbers and there were no significant deviations in the observed results by increasing the number of iterations any further.)

Figure 1: Comparison Report showing average time taken (ms) in processing XML files of various sizes using most commonly used alternatives/libraries.

Analysis of Test Results & Recommendations

We observed the following results from the tests and make corresponding recommendations for the various alternatives:

Java Deserialization turned out to be the fastest among all techniques (except for files of very small size where the overhead of native Java Deserialization process made it the slowest).

Recommendations: Java Serialization performed the fastest among all the alternatives. However serialized data is in native binary format and is linked to a version of the compiled code which leaves it un-portable between different compilations. This is a big drawback especially when the data needs to be used by different modules of a distributed enterprise application and when continuous development/enhancement to the underlying source code is a given fact for any application. Also, the serialized data being in native binary format leaves it not readable by any editor without being deserialized by the Java Serialization framework and this counts as a big drawback as well.

Hence we do not recommend using Java Serialization and other binary formats except for fairly stable and small applications.
FastInfoSet library performed considerably slower than other alternatives and performed the slowest overall. Generally seen as a library which can be used for faster processing of data, the results show that the overhead of using the FastInfoSet data structures by the FastInfoSet library makes it the slowest technique to be used. Test results shows that FastInfoSet performed almost 2X times slower than JAXB and 3X times slower than native Java Deserialization.

We observed that FastInfoSet performed slower even when we used the highest level of compression using the ZLIB compression library and processed the compressed data stream (effectively we added the time to decompress the data to JAXB tests, for a meaningful comparison with FastInfoSet).

Recommendations: FastInfoSet library performed the slowest of all the alternatives in processing of the data. However it also compressed the data to small size, reducing the time taken to transport the data -over the wire and in the storage footprint. As an example, an input XML file of 400,384 bytes was converted into compressed binary XML format of only 40,451 bytes, which is a significant reduction.*

It is also important to understand that unlike the case of Java Deserialization where the data is converted into unreadable binary format, the compressed binary variant of FastInfoSet is actually binary XML and can be easily read and selectively bound using StAX filters and is also interoperable with .NET.

Hence we would recommend use of FastInfoSet only in case you are more concerned with size of data on the wire and disk storage and are less concerned with processing time; where FastInfoSet clearly is working slowest as compared with other alternatives."

*(Table 2 below shows that compressing raw data directly leads to much smaller size as compared to FastInfoSet. The underlying data in FI is compressed binary stream which can be read using StAX filters)
JAXB performed considerably faster than FastInfoSet and slightly slower than Java Deserialization. DOM has its own advantages and disadvantages, but the overall flexibility offered by JAXB makes it the most viable option. Basically, JAXB has two phases, code generation and parsing. You can either use the JAXB XJC compiler to auto generate all the Java objects based on the types defined in the corresponding XML Schema or write all the Java objects mapping to XML types on your own. The -auto generation of code is a great time saver and productivity boost due to correct mapping of XML types to the corresponding Java classes being generated.

Also, since JAXB works directly on the XML text data, there is no binary format involved and the XML text can be selectively evaluated or read on demand without any involvement of the JAXB framework.

Recommendations: JAXB is our recommended choice. It's slightly slower speed compared to Java Deserialization is more than compensated by the advantages of code generation based on an XML schema and by its ability to do runtime binding of the XML to any version of the source code. JAXB also scores high in our recommendation due to its ability to process and read XML as raw text."
DOM parser performed slightly faster than JAXB and slightly slower than Java Deserialization for files of larger size. For smaller files DOM parser was the fastest.

Recommendations: As mentioned earlier, DOM parser can be used if an XML document is not too large and we want the entire XML available in memory for data manipulation. DOM parses the whole document and constructs a complete document tree in memory before it returns control to the client (best way to think of DOM is as a map of maps). Even DOM parsers that employ deferred node expansion, and thus are able to parse a document partially, have high resource demands because the document tree must be at least partially constructed in memory. Also with DOM you have to do all the processing like converting numeric data into a binary representation, etc.

Hence we do not recommend DOM except for very small XML files and in situations where memory footprint is not a concern

Conclusion - Is XML Slow?

We have shown in this article that XML is generally not slow, and it depends a lot on the technology being used. Even though DOM (Xerces) is on average 25% faster, JAXB is still the recommended choice when considering all the work that the JAXB unmarshaller has to do, like converting numeric data into a binary representation, etc. which, for many applications, would be eventually needed anyhow after the XML is loaded as a DOM tree. XML is not much slower than the alternative no-loss transmission mechanisms, but its capabilities of being so versatile and readable makes it a better choice for any enterprise application.

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Snake Oil Salesmen, Java, General Relativity and Low-Latency Trading

java7developer — Wed, 09 Mar 2011 11:47:50 -0500

I've always wanted to write a post which had that as the title.

Sharp practices abound in this world, and one of the most disturbing aspects to them is the extent to which the media (and people in general) uncritically repeat "information" or "news" that is really just a press release by a commercial interest.

So, I was pleased to see the launch of Churnalism (http://churnalism.com/), a website where you can cut and paste the text of a news "story" and see how much of it was pulled, verbatim, from a press release.

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Welcome to Java Tutor

Jeff Friesen — Thu, 24 Feb 2011 21:00:31 -0500

Hello. I'm Jeff Friesen and I welcome you to Java Tutor, a new blog that I'm writing for JavaWorld. Java Tutor is my platform for teaching about Java 7+ (the standard edition, in terms of language, APIs, architecture, and tools) and JavaFX 2.0+ (which eventually will be integrated into Java standard edition, probably starting with version 8). I teach about these technologies mainly via programming projects (e.g., multiple key press detection).

I welcome your input to this blog, and will write about relevant topics that you suggest.

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Tomorrow’s Tech Today: HTML 5 by Scott Davis at GIDS 2011

sapna123 — Mon, 17 Jan 2011 05:45:42 -0500

As software engineers, we take comfort in the idea of concrete specifications. As web developers, our hearts are either broken (frequently!), or we recognize the W3C's role is a delicate balance of leading the browser developers in new and exciting directions while, in their own words, "paving over the cow paths" of existing, de facto standards. Scott Davis is coming back this summer to the fourth season of India's biggest summit for the software developer ecosystem - Great Indian Developer Summit to talk on HTML 5 and its features.

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Core Java

Easy ORM-ness for GAE, part 2

Andrew Glover — Tue, 28 Dec 2010 16:32:45 -0500

As I’ve blogged and written about on various occasions, Google App Engine doesn’t just scale apps: it can also help you assemble them rapidly, using slick tools. Part 2 of “Twitter mining with Objectify-Appengine” wraps up the domain model for a Twitter-mining application, adding hooks for indexing and caching.

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.NET eye for the Java guy

Andrew Glover — Fri, 17 Dec 2010 15:21:47 -0500

I recently had the pleasure of catching up with my old friend, Ted Neward. As anyone who has ever had the occasion of inquiring into Ted’s opinions knows, Mr. Neward is a veritable fire hose of technical knowledge intermixed with random thoughts, name dropping, and rants, all of which makes a conversation with Ted unpredictable, and yet, a lot of fun.

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From OAK to JAVA

somanathtv — Sat, 11 Dec 2010 00:19:59 -0500

From OAK to JAVA
I like to follow history behind computers and programming languages and I also wondered how peoples inventing or creating operating systesm or programming languages. One another thing amazed me is the way JAVA evolved (See the history in PPT) and how Green team at Sun arrived the name so called "JAVA". See below email from Gosling to Jonathan (copied from Jonathan's blog)
--------------------------------------------------------------------
From: James Gosling
Date: August 24, 2007 8:16:58 PM PDT
To: Jonathan Schwartz

Subject: How was Java named?

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Java Beginner

SQL for the NoSQL

Andrew Glover — Wed, 01 Dec 2010 09:31:29 -0500

But there is one slight issue with NoSQL. You can’t use SQL.

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JSON-able domain objects

Andrew Glover — Mon, 15 Nov 2010 19:25:10 -0500

JSON has arguably become the new lingua franca of the Internet; that is, JSON has become preferable for browser to server communication — over that of XML, which, as it happens, is quite verbose. JSON’s lightweight-ness makes it easily readable and easy to parse.

For example, in the case of a Retweet object (which represents a Twitter retweet), I can represent it easily enough in JSON like so:

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Easy ORM-ness for GAE

Andrew Glover — Thu, 11 Nov 2010 14:47:50 -0500

Objectify-Appengine is one of an emerging class of tools that extend the convenience of NoSQL, in this case by providing a Hibernate-style mapping layer between your application and the GAE datastore.

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This dependency injection madness must end!

Johannes Brodwal — Wed, 10 Nov 2010 15:00:39 -0500

Or: Poor man’s dependency injection: Singleton-initialized field

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Video: No-red refactoring

Johannes Brodwal — Fri, 05 Nov 2010 03:00:35 -0400

The more I code, the more I’ve learned to appreciate keeping the code clean even during complex refactorings. By “clean”, I mean that the code always compiles and the test always run.

I often find myself in a situation where I have a method call that’s starting to accumulate parameters. Something like this:

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Cross-cutting code, the homemade way

Johannes Brodwal — Tue, 26 Oct 2010 09:00:24 -0400

I though I’d do something different this time. Instead of describing something technical, I have recorded a five minute video that shows a very neat trick in Java: How to create a bit of code that wraps existing method calls to an object with any behavior you may desire.

This is nothing new, but I’ve noticed that not many developers know how to use it, so I hope this video may be useful:

Gaelyk stories are easyb

Andrew Glover — Mon, 25 Oct 2010 13:21:01 -0400

On the heels of easyb’s newest release and the addition of a Google App Engine plugin for easyb comes another plugin: easyb-gaelyk. Briefly,

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App Engine stories are easy

Andrew Glover — Fri, 22 Oct 2010 13:07:17 -0400

With the release of easyb 0.9.8, a new plugin has hit the streets that enables easyb to more easily verify Google App Engine applications running locally.

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easyb team releases 0.9.8

Andrew Glover — Wed, 20 Oct 2010 13:39:27 -0400

The easyb team is proud to announce the release of easyb 0.9.8! easyb 0.9.8 includes a host of new features, many of which are available due to the reworking of story execution by Richard Vowles. easyb stories are now executed in logical order rather than sequential; thus, for example, after type clauses can be defined anywhere in a story. Shared stories now work across files too.

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Eclipse telepathy: Your IDE can guess what you want

Johannes Brodwal — Thu, 14 Oct 2010 06:00:37 -0400

Ctrl-1 is the magic “do what I think” button in Eclipse. Whenever I press it, Eclipse seems to come up with something that’s helpful in the current context. In this blog post, I illustrate 10 things that Eclipse hide under the ctrl-1 keypress. This is a follow up on my post on Eclipse stenography.

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Discussing the role of an architect

Andrew Glover — Tue, 12 Oct 2010 09:21:43 -0400

My friend Ken Sipe often gives a presentation entitled “So you want to be an Architect” where he explores the role of an architect — a lot of people attend this talk so I was most interested in catching up with him to discuss this subject in more detail.

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MongoDB conversation

Andrew Glover — Mon, 04 Oct 2010 14:37:46 -0400

Not long ago, I had the distinct pleasure of chatting with Eliot Horowitz, the CTO of 10gen (the commercial company behind MongoDB). In this podcast, Eliot talks about MongoDB, which is a scalable, high-performance, open source document database. Eliot does a wonderful job of describing how MongoDB can fit into your toolkit and how it differs from alternatives like CouchDB.

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