Develop Reference

Java check if program is installed on windows

Is there a way to check if a specific program is installed on Windows using Java?
I'm trying to develop a Java program that automatically creates zip archives by using the code line command from 7-Zip.
So, I would like to check in Java if on my windows OS '7-Zip' is already installed. No check for running apps or if OS is Windows or Linux. I want to get a bool (true/false) if '7-Zip' is installed on Windows.

The library Apache Commons has a class called SystemUtils - full documentation is available at https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/SystemUtils.html.
In this library you have the following static boolean properties at your disposal:
SystemUtils.IS_OS_LINUX
SystemUtils.IS_OS_WINDOWS

The unix-like solution would be to simply try to run the program with --version flag (on windows probably the /? or - like in the 7zip case - without any at all) and check whether it fails, or what the return code will be.
Something like:
public boolean is7zipInstalled() {
try {
Process process = Runtime.getRuntime().exec("7zip.exe");
int code = process.waitFor();
return code == 0;
} catch (Exception e) {
return false;
}
}

I assume that you're talking about Windows. As Java is intended to be a platform-independent language and the way how to determine it differs per platform, there's no standard Java API to check that. You can however do it with help of JNI calls on a DLL which crawls the Windows registry. You can then just check if the registry key associated with the software is present in the registry. There's a 3rd party Java API with which you can crawl the Windows registry: jRegistryKey.
Here's an SSCCE with help of jRegistryKey:
package com.stackoverflow.q2439984;
import java.io.File;
import java.util.Iterator;
import ca.beq.util.win32.registry.RegistryKey;
import ca.beq.util.win32.registry.RootKey;
public class Test {
public static void main(String... args) throws Exception {
RegistryKey.initialize(Test.class.getResource("jRegistryKey.dll").getFile());
RegistryKey key = new RegistryKey(RootKey.HKLM, "Software\\Mozilla");
for (Iterator<RegistryKey> subkeys = key.subkeys(); subkeys.hasNext();) {
RegistryKey subkey = subkeys.next();
System.out.println(subkey.getName()); // You need to check here if there's anything which matches "Mozilla FireFox".
}
}
}
If you however intend to have a platformindependent application, then you'll also have to take into account the Linux/UNIX/Mac/Solaris/etc. (in other words: anywhere where Java is able to run) ways to detect whether FF is installed. Else you'll have to distribute it as a Windows-only application and do a System#exit() along with a warning whenever System.getProperty("os.name") is not Windows.
Sorry, I don't know how to detect in other platforms whether FF is installed or not, so don't expect an answer from me for that ;)

Opening a TCL gui within Java code

I have a TCL file which uses Tcl's BWidget package that I've been using as a GUI for my program. I now want to be able to load up this GUI from a separate Java program. I've looked into Jacl and Swank, but they don't seem to do exactly what I want.
I've tried the following with Jacl but it's unable to evaluate the file. While debugging, I can see that it completes parsing my tcl file, but it throws an exception while parsing through the BWidget package tcl files. Here's my Java code:
Interp interp = new Interp();
try {
interp.evalFile("C:\\CTP\\Tcl\\LuxonCtp32.tcl");
} catch (TclException ex) {
int code = ex.getCompletionCode();
System.err.println("command returned bad error code: " + code);
} finally {
interp.dispose();
}
Any ideas on how I can accomplish what I want to do? Is it even possible?

Tcl itself can not display a GUI. It uses a plugin called Tk for that.
In the C reference implementation of Tcl you get Tk as well.
Tk has not been ported to Java, Tcl has.
You can not use Jacl to display Tk widgets, but TclBlend could do that, because TclBlend uses the C reference implementation of Tcl. That means that the user needs a working Tcl/Tk installation.
There are some problems with TclBlend and Tcl > 8.5 through, which result in a segfault.
IIRC you have to remove the conditional if around Tcl_FindNameOfExecutable in TclBlends C code (and compile it yourself).

Go to this site http://jtcl-project.github.io/jtcl/ and download now for the binary zip. Its a recent java tcl on github called Jtcl.
Unzip it and you will find a jar called jtcl-2.7.0.jar.
I am using Netbeans 8 my preference.
I add the jar into Project Library.
I create a java file called JTclHallo.java and this is the code.
package jtclhallo;
// import tcl.lang it belongs to jtcl-2.7.0 jar a must
import tcl.lang.*;
// Java wrapper to test JACL or JTCL.
public class JTclHallo {
public static void main(String []args) {
//Interp is a java class belonging to tcl.lang. Unrar the jtcl-2.7.0
Interp i = new Interp();
try {
//call your tcl file mine was swing.tcl from the E drive
i.eval("source E:/private/swing.tcl");
} catch (TclException e) {
System.out.println("Exception: " + e.getMessage());
}
}
}
For swing.tcl
package require java
set window [java::new javax.swing.JFrame]
$window setSize 600 400
$window setVisible true

Webpage Java Applet - Open On Screen Keyboard

I'm trying to open the On Screen Keyboard from within a web application on a touch screen interface. I am using Opera as the browser for the built in "Kiosk" features, but it does not support VBScript- an easy way of openning a .exe file from a webpage.
I know Java can be ran from within a web page and it can also be used to open another application, such as the OSK!
Below is my working Java code:
package runtimeexec;
import java.io.IOException;
public class RuntimeExec {
public static void main(String[] args) {
try {
Runtime runTime = Runtime.getRuntime();
Process process = runTime.exec("cmd /c osk");
} catch (IOException e) {
e.printStackTrace();
}
}
}
Now I want to embed this into a webpage, so that it can open the osk. My .class file is at http://theyconfuse.me/java/runtimeexec/RuntimeExec.class and my current attempt to embed this code is at http://theyconfuse.me/java/ with the following embed code:
<applet codebase="http://theyconfuse.me/java/runtimeexec" code="RuntimeExec.class" width="200" height="200"></applet>
How ever, when I load the page, I get the following:
NoClassDefFoundError
RuntimeExec (wrong name: runtimeexec/RuntimeExec)
Can anyone help me with what am I missing here? Thanks

code="RuntimeExec.class"
Should be with package structure, separated by dots, but without the .class extension.
code="runtimeexec.RuntimeExec"

Trouble with ProcessBuilder

Following code opens status very fine in notepad:
import java.util.*;
class test
{
public static void main(String args[])
{
try{
ProcessBuilder pb=new ProcessBuilder("notepad","F:/status");
pb.start();
}catch(Exception e)
{
System.out.println(e);
}
}
}
Following code does'not play the song:
import java.util.*;
class test
{
public static void main(String args[])
{
try{
ProcessBuilder pb=new ProcessBuilder("C:/Program Files (x86)/VideoLAN/VLC/vlc","D:/02 Tu Jaane Na");
pb.start();
}catch(Exception e)
{
System.out.println(e);
}
}
}

I think that the problem is that you're ignoring the fact that the files you're trying to open have filename extensions.
Windows Explorer doesn't display file extensions by default - that is probably why you are not aware of their existence.
The reason why notepad worked in your first example is that notepad automatically adds .txt extension to its filename parameter in case you didn't provide one yourself. So in reality the file that is being open is not status but status.txt.
VLC doesn't have this "advanced" functionality because there's no specific filename extension it is designed to work with.
So you will need to look up the dir command output and add the full file name as a parameter.
If that was the real issue - you might want to modify your Windows Explorer settings for it to display file extensions:
or, which is better, switch to a more programmer-friendly OS :)

For 1.6+ code, use Desktop.open(File) instead.
Of course, the sensible thing to do immediately before calling that is to check File.exists().
OTOH, Desktop.open(File) throws a slew of handy exceptions, including:
NullPointerException - if file is null
IllegalArgumentException - if the specified file doesn't exist
UnsupportedOperationException - if the current platform does not support the Desktop.Action.OPEN action
IOException - if the specified file has no associated application or the associated application fails to be launched
Properly handled, the exception would indicate the immediate problem.
As an aside, the Desktop class is designed to be cross-platform, and will handle any file type for which an association is defined. In that sense it is a lot more useful for something like this, than trying to use a Process.

How to open user system preferred editor for given file?

I'm trying to figure out how to open the system preferred editor for a given file.
Say, we have a file manager, written in Java. User goes to folder and sees the list of files. And, for example, there is a file Icon.jpg. User double clicks on the filename and file opens in system's preferred editor (i.e. Gimp). The main issue is - how to do that?
We can do Runtime.getRuntime().exec("something file"), but this way you should know which program is preferred in user environment. But how?
We also are able to do Desktop.getDesktop().edit(File file), but this way we cannot track process and aren't able to know then this child process is closed. Other issue - function doesn't work on linux (at least on Ubuntu 8.10). There is also Desktop.getDesktop().open(File file), but it forces to open file viewer, instead of system viewer for that file type.
I am searching for a solution all week, but didn't got any suitable and generic one. Do you know the other approaches to this question? For my project it would be enough if it would work on Windows+Linux+Mac.
Thank you for your answers and advices.
Edit on 2009-02-08 23:04
Other suggestion: can I force "application selection" window in Windows and in Linux, as in Mac with "open file"? For example, then you trying to open file, you are being asked to choose application from list of system preferred ones? (something like "Open with..." in Windows explorer). Do you know?

Seems that if you can't use java.awt.Desktop you have to distinguish between the OSes:
Windows:
RUNDLL32.EXE SHELL32.DLL,OpenAs_RunDLL <file.ext>
Linux:
edit <file.ext>
Mac:
open <file.ext>
HTH. Obviously, that is not very portable...

Check out the java.awt.Desktop object. In your case, you want to invoke edit()
If you want to ensure that a given platform supports this call, then you can do something like the following (I have not tested this code):
public boolean editFile(final File file) {
if (!Desktop.isDesktopSupported()) {
return false;
}
Desktop desktop = Desktop.getDesktop();
if (!desktop.isSupported(Desktop.Action.EDIT)) {
return false;
}
try {
desktop.edit(file);
} catch (IOException e) {
// Log an error
return false;
}
return true;
}

This isn't cross-platform, but on Mac OS X you can do
Runtime.getRuntime().exec("open filename");
The open(1) executable uses LaunchServices to pick the right program to execute, and then uses that to open the file named filename.

This will work in windows
Runtime.getRuntime().exec( "CMD /C START filename.ext " );

For JavaFX applications, we can use HostServices. This question covers how to use HostServices. This should work on Ubuntu (tested)/Windows (not tested) and Mac (not tested).
import java.io.File;
import java.io.IOException;
public class App extends Application {
}
File file = new File("/your/file/path");
HostServices hostServices = getHostServices();
hostServices.showDocument(file.getAbsolutePath());
getHostServices() is a method of JavaFX Application class.