Java I/O FAQ   

This page is the FAQ for the "I/O and Streams" forum. It's editable by everyone, so add your own content as you see fit.

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Other FAQ pages that deal with I/O

• AccessingFileFormats - How to read and write various file formats

• ByteArrayBuffer - a class to read and write primitives from a byte array

• ReadDoesntDoWhatYouThinkItDoes

• AvailableDoesntDoWhatYouThinkItDoes

• How do I EditAnExistingFile

• The FileUpload page has hints on how to upload files to a server via FTP, SMB and HTTP.

• I'm getting a TooManyOpenFiles exception

• WhoisLookup - how to perform a whois lookup programmatically

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Links to articles elsewhere that relate to I/O

• A good introduction to Unicode: The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) by Joel Spolsky

• Character Conversions from Browser to Database

• Changes in Java 5.0 for handling Unicode characters above 65535: John O'Conner Tom White Surrogates

• Overview of the java.nio package - nonblocking I/O

• Don't println to a Socket - some good hints on how not to do socket communication

• How to read the Windows Registry

• USB: How to access USB devices - Access USB devices from Java applications - Java wrapper for the libusb and libusb-win32 USB library - code examples - jUSB library - libusb4j library - javax.usb

• How to implement SSH, SFTP and SCP in Java: Ganymed SSH-2 for Java - JSch

• Connect through a Proxy

• Using ICMP packets (for ping and traceroute) in Java: Jpcap library

• JNetPcap - library for network packet capture and analysis

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Where can I get an implementation of the javax.comm API for Windows?

Sun does not provide an implementation of javax.comm version 3 for Windows, but version 2 can be used in conjunction with RXTX; see the javax.comm download page for further information. Other options (which do not implement the javax.comm API) are

• RXTX (open source)
• icaste JCommSerial (commercial)
• SerialPort (commercial, X/Y/ZModem and Kermit implementations are also available)

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How can I set the client timeout when making an URL connection?

Starting with Java 5, this functionality is available in the JavaDoc:java.net.URLConnection class and its subclasses (like HttpURLConnection) via the getConnectTimeout/setConnectTimeout methods. For older Sun JVMs, a workaround is described here.

Jakarta Commons HttpClient also supports setting a timeout.

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How can I check the type of an image file?

The freely available ImageInfo class can identify certain image types: JPEG, PNG, GIF, BMP, PCX, IFF, RAS, PBM, PGM, PPM and PSD. It also determines certain image properties like height, width and color depth.

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How can I send SMS from a Java application?

You'll need an SMS library like smsj, SMSLib or smstools and a provider. You can find the latter by googling for "bulk sms http". This article may also be of interest.

Many cellular providers make an email-to-SMS gateway available. Here are the email addresses for several US providers:

• T-Mobile: phonenumber@tmomail.net
• Virgin Mobile: phonenumber@vmobl.com
• Cingular: phonenumber@cingularme.com
• Sprint: phonenumber@messaging.sprintpcs.com
• Verizon: phonenumber@vtext.com
• Nextel: phonenumber@messaging.nextel.com

where phonenumber = your 10 digit phone number

I would probably not use this gateway for bulk message as the providers no doubt have measures in place to prevent abuse.

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How can I use a modem from within Java? (or, to put it in another way, is there an implementation of JTAPI?)

The http://xtapi.sourceforge.net/ project "has providers for Microsoft’s TAPI, Serial Voice Modems, and Voice Over IP utilizing the OpenH323? Projects H.323 stack implementation".

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How can I determine the encoding of a given file?

That's what the jchardet and juniversalchardet libraries do.

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CategoryFaq