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CMP File I/O Amanuensis

Unfortunately, Oracle has effectively decommitted Applets. This means you can no longer run the various CMP programs in a browser. You must download them and install them. You must have the most recent Java JRE (Java Runtime Environment) 1.8.0_131 32-bit or 64-bit. It no longer matters which browser you use.
Oracle has effectively decommited Applets, so this Applet will no longer run online in your browser, but it is a hybrid you can also download, install and run it on your own machine as standalone application. It will start and run faster if you do that. It will also work safely even if you have disabled Java in your browser.

Introduction Buffer Size
The Applet Acquiring
Requirements and Troubleshooting Links


This Applet will help you write Java code. Instead of memorising the dozens of I/O classes and methods, just select what you want to do and let the amanuensis generate the code, then paste it into your source. Please pass on bugs and suggestions for improvement. The code is messy, but this just reflects the chaos in Oracle’s design of It is a bit like doing jig-saw puzzles trying to find ways to fit the classes together. The asymmetry is astounding.

The 2007-08-05 version was a major rewrite. There are undoubtedly errors in the code it generates, though I can guarantee all code it generates will at least compile. It is a huge program with fiendishly baroque interactions. It is perhaps the most difficult to debug and proofread program I have ever written. Please report any errors in the code in generates or suggestions for improvement. The most likely errors is it will give you a roundabout way to do something that can be specified more directly.

The File I/O Amanuensis does not yet give you any help with the Java 1.4+ javax.imageio.ImageIO class or the java.nio classes: Buffer, ByteBuffer, ByteOrder, CharBuffer, DoubleBuffer, FloatBuffer, IntBuffer, LongBuffer, MappedByteBuffer or ShortBuffer.

Nio is particularly useful when you have:

Binary is a compact, machine-friendly, human-unintelligible format. For human readable i/o, Java works with Strings of characters. You separately convert these to and from internal binary format e.g. int. See the conversion Amanuensis for how.

The Applet

Applet failed to run. No Java 1.8 or later plug-in found.

Java Requirements and Troubleshooting

FileIO is a signed Java Applet (that can also be run as an application) to File I/O Amanuensis. You are welcome to install it on your own website. If it does not work…
  1. For this Applet hybrid to work, you must click grant/accept/always run on this site/I accept the risk to give it permission to let you copy/paste. If you refuse to grant permission, the program may crash with an inscrutable stack dump on the console complaining about AccessController.checkPermission.
  2. In the Java Control Panel security tab, click Start ⇒ Control Panel ⇒ Programs ⇒ Java ⇒ Security, configure medium security to allow self-signed and vanilla unsigned applets to run. If medium is not available, or if Java security is blocking you from running the program, configure high security and add to the Exception Site List at the bottom of the security tab.
  3. Often problems can be fixed simply by clicking the reload button on your browser.
  4. Make sure you have both JavaScript and Java enabled in your browser.
  5. Make sure the Java in your browser is enabled in the security tab of the Java Control panel. Click Start ⇒ Control Panel ⇒ Programs ⇒ Java ⇒ Security ⇒ Enable Java Content in the browser.
  6. This signed Java Applet (that can also be run as an application) needs 32-bit or 64-bit Java 1.8 or later. For best results use the latest 1.8.0_131 Java.
  7. You also need a recent browser.
  8. It works under any operating system that supports Java e.g. W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32, W10-64, Linux, LinuxARM, LinuxX86, LinuxX64, Ubuntu, Solaris, SolarisSPARC, SolarisSPARC64, SolarisX86, SolarisX64 and OSX
  9. You should see the Applet hybrid above looking much like this screenshot. If you don’t, the following hints should help you get it working:
  10. Optionally, you may permanently install the Canadian Mind Products code-signing certificate so you don’t have to grant each time.
  11. If the above Applet hybrid appears to freeze-up, click Alt-Esc repeatedly to check for any buried permission dialog box.
  12. If you have certificate troubles, check the installed certificates and remove or update any obsolete or suspected defective certificates. The only certificate used by this program is mindprodcert2017rsa.cer.
  13. Especially if this Applet hybrid has worked before, try clearing the browser cache and rebooting.
  14. To ensure your Java is up to date, check with Wassup. First, download it and run it as an application independent of your browser, then run it online as an Applet to add the complication of your browser.
  15. If the above Applet hybrid does not work, check the Java console for error messages.
  16. If the above Applet hybrid does not work, you might have better luck with the downloadable version available below.
  17. If you are using Mac OS X and would like an improved Look and Feel, download the QuaQua look & feel from UnZip the contained quaqua.jar and install it in ~/Library/Java/Extensions or one of the other ext dirs.
  18. Upgrade to the latest version of Internet Explorer or another browser.
  19. Click the Information bar, and then click Allow blocked content. Unfortunately, this also allows dangerous ActiveX code to run. However, you must do this in order to get access to perfectly-safe Java Applets running in a sandbox. This is part of Microsoft’s war on Java.
  20. Try upgrading to a more recent version of your browser, or try a different browser e.g. Firefox, SeaMonkey, IE or Avant.
  21. If you still can’t get the program working click the red HELP button below for more detail.
  22. If you can’t get the above Applet hybrid working after trying the advice above and from the red HELP button below, have bugs to report or ideas to improve the program or its documentation, please send me an email atemail Roedy Green.
Java powered   Get New Java   Get New Browser   Help


Don’t embed FileIO’s snippets directly into your programs. Encapsulate them in small methods and use those. Your programs will be easier to understand and maintain. Further, if you find a better way to do somethming, you will have to fix it in only one place.

Buffer Size

Everybody knows that increasing buffer size increases I/O speed, but how you do allocate your buffer space between the InputStream and the Reader? I discovered by experiment 50:50 is optimal. This means if you are willing to allocate 100K bytes buffer space overall, you should give 50K bytes to the InputStream and 50K bytes / 25K characters to the Reader. If you want extreme speed, you can read an entire file at once into RAM (Random Access Memory) with HunkIO.


File I/O Amanuensis
6.2 2014-05-10 free Java
more infoprecisscreenshotbrowse source repository
for the current version of File I/O Amanuensis.
Applet to show you how write Java I/O code to read and write files, URLs, HTTP CGI/GET/POST, sockets, StringReaders, resources etc. You select what sort of I/O you need and it generates the Java source code.
download 719K zip for File I/O Amanuensis Java source, compiled class files, jar and documentation to run on your own machine either as an application or an Applet.

Runs on any OS that supports Java e.g. W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32, W10-64, Linux, LinuxARM, LinuxX86, LinuxX64, Ubuntu, Solaris, SolarisSPARC, SolarisSPARC64, SolarisX86, SolarisX64 and OSX.

First install the most recent Java.

To install, extract the zip download with WinZip, (or similar unzip utility) into any directory you please, often J:\ — ticking off the use folder names option.

To check out the corresponding source from the Subversion repository, use the TortoiseSVN repo-browser to
access fileio source in repository with [Tortoise] Subversion client on

After you have installed the jar, you can run it as an application. Type:

java -jar J:\com\mindprod\fileio\fileio.jar

adjusting as necessary to account for where the jar file is.

download ASP PAD XML program description for the current version of File I/O Amanuensis.

$1989.00 US donated so far. If the CMP utilities solved your problem, please donate a buck or two, or donate to one of the charities featured in the footer public service ads throughout the website and get a tax receipt.

File I/O Amanuensis is free. Full source included. You may even include the source code, modified or unmodified in free/commercial open source/proprietary programs that you write and distribute. Non-military use only.
amend a file
Comparable/Comparator Cutter Amanuensis
Conversion Amanuensis
Files and directories
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Quoter Amanuensis

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