Develop Reference

Java 8 on Big Sur reports os.name as "Mac OS X" and os.version as "10.16"

Is it just my setup or is anyone else having this problem?
Using AdoptOpenJDK 1.8.0_275 installed at:
/Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home/jre
API docs of System.getProperties() do not specify any details.

Can confirm this is still happening on adoptopenjdk14, as well as openjdk early access build for j16.
You can file a bug if you want, but I bet it'll be denied. At this point, the name Mac OS X is not so much 'the name of the OS' as a 'globally agreed upon keyword identifying that unix-based mac operating system', where I mean globally literally (as in, 'around the planet', not 'across your source base/VM'). Changing it would just break stuff needlessly. The same applies, to a lesser degree, to version 10.16: The thing before the dot is not so much 'this is how the OS identifies itself' and more a 'globally agreed upon versioning scheme for Mac OS, identifying a wide and ill defined set of capabilities'.
There is no meaningful difference between the transition between big sur and catalina, other than the fact that apple made a marketing decision. If you want to point at an OS transition that might warrant the entirely nebulous choice to consider it a 'major change', surely it was the one to catalina, as that made by far the largest changes (including removing support for 32-bit entirely) in the last bunch of releases.
This leaves you with the challenge of: Okay, great, I can use System.getProperty("os.name") to get the globally agreed upon keyword that means unix-like Mac OS, and os.version for a string I can break into bits to figure out some nebulous batch of capabilities, but what if I need the actual name of the OS to e.g. show to a user?
Then you have three major options:
The easy one is to just write mapping code. Acknowledge that os.name and os.version give you (rather arguably) useful intent and not so much official names, and therefore, write some mappings. These would map name/version pairs to rendering strings, falling back to just printing the name string and the version string, concatenated, verbatim. You could add a mapping: Mac OS X/10.16 → Mac OS Big Sur in this table.
The hard way: Figure out you're on a mac (which is now easier; os.name returns Mac OS X, or just check for the existence: Files.isExecutable(Paths.get("/usr/bin/sw_vers"))), and then use ProcessBuilder to execute /usr/bin/sw_vers, picking up all output into a big string, and then parse it. Its output looks like:
ProductName: macOS
ProductVersion: 11.1
BuildVersion: 20C69
which, crucially, doesn't even include the words Big Sur, but does give you 11.1. I don't know how to run a command line tool that actually gives you Big Sur. Maybe system_profiler, but note that this takes many minutes to run, I really doubt you want to run that.
NB: you can also run .command("/usr/bin/sw_vers", "-productVersion") which gives you just 11.1, this may be a lot simpler to parse. -productName also works, gives you just macOS.
If you need this information to scan for OS capabilities, then stop doing this. It doesn't work with browsers, and it's not a good plan for OS releases either. What capability are you scanning for? Imagine, for example, if it is 'Can I run /usr/bin/sw_vers to figure stuff out', as a hypothetical example. The right strategy is NOT to check os.name/os.version, conclude that the command must exist, and then run it, failing catastrophically if it is not there. The right move is to check if /usr/bin/sw_vers exists, and then execute it, falling back to some non-mac based solution (perhaps /usr/bin/uname) in other cases. Scan for the capability, don't scan for the OS/version.

Java code to call native tool sw_vers
Regarding Option # 2 in the Answer by rzwitserloot, here is a complete code example to run from Java a command-line tool sw_vers that describes the version of macOS software running on the host computer.
If on the command-line (console) such as in Terminal.app, you run:
sw_vers
…in Big Sur on an Intel Mac we get:
ProductName: macOS
ProductVersion: 11.2
BuildVersion: 20D64
We only need the middle piece. So running:
sw_vers -productVersion
…shows simply 11.2, the value we need for your purpose.
Here is complete example app with a method to return this string into Java.
ProcessBuilder class creates operating system processes. Each new process is represented by the Process class.
We use try-with-resources syntax to automatically close the InputStream and Scanner objects.
Once you have the 11.2 string in hand, split on the FULL STOP, pull the first number 11, and you know you are running on Big Sur.
package org.example;
import java.io.IOException;
import java.io.InputStream;
import java.util.*;
/**
* Example code showing how to get current version of macOS from Java
* by running a native command-line tool `sw_vers`.
*/
public class App
{
public static void main ( String[] args )
{
App app = new App();
app.demo();
}
private void demo ( )
{
String version = this.getMacOsVersionNumber();
System.out.println( "version = " + version );
}
public String getMacOsVersionNumber ( )
{
String result = "";
List < String > command = List.of( "sw_vers" , " -productVersion" );
try (
InputStream inputStream = new ProcessBuilder( command ).start().getInputStream() ;
Scanner s = new Scanner( inputStream ).useDelimiter( "\\A" ) ;
)
{
result = s.hasNext() ? s.next() : "";
}
catch ( IOException e )
{
e.printStackTrace();
}
return Objects.requireNonNull( result );
}
}

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 ;)

Java's "os.name" for Windows 10?

In Java, we can see the property value of os.name to know the name of the underlying operating system: System.getProperty("os.name").
For each edition of Windows, it used to return always the exact name of the OS: Windows XP for XP, Windows Vista for Vista, Windows 7 for Seven, Windows 8.1 for 8.1, and so on...
The problem is: I just updated my Windows 8.1 to Windows 10 using the released Microsoft updater, and it seems like this property still remains Windows 8.1:
public class OSTest {
public static void main(String[] args) {
System.out.println(System.getProperty("os.name"));
}
}
How can I create a workaround for this? And, does anyone know if this problem persists if installing a fresh Windows 10 copy - that is, this bug is caused by the Microsoft auto-updater -?

This is a known problem JDK-8066504 that has been fixed in upcoming Java 8 update 60.
The reason is GetVersionEx function has changed its behavior since Windows 8.1.
There are multiple possible workarounds, see MSDN article.
The trivial one is to exec cmd.exe /c ver.
The other is to look at the version information of one of the system files, e.g. kernel32.dll.

This is definitely a known bug. It occurs because the os.name property gets its value from the GetVersionEx in the source code of the Windows API. GetVersionEx however,
may be altered or unavailable for releases after Windows 8.1
As per Microsoft's official website. Instead, we will need to use the IsWindows10OrGreater found in the Version Helper API functions in the versionhelpers.h file. As you probably guessed though, this file is not a Java file, it is written in C. As a result we need to include it in a somewhat roundabout way. It does take quite a bit of work (you need to program in JNI :/) but this tutorial will help you do it. Another solution is shown in this bug log, and does require less effort.

I faced the same issue, used the following workaround:
The cmd command "systeminfo" returns "OS Name:" which is the right name for the OS, wrote the following function for this:
private boolean os2k10Check()
{
try{
Process p = Runtime.getRuntime().exec("systeminfo"); /*Execute cmd command "systeminfo"*/
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while (true)
{
line = r.readLine();
if (line == null) { break; }
if(line.contains("OS Name:")) /*If output contains OS Name and 2010*/
{
if(line.contains("2010"))
return true;
else
return false;
}
}
}
catch(Exception e)
{System.out.println("Platform Type: os2010check: exception"+e);}
return false;
}

Hm... I don't know if it is a fix of Windows 10(10.0.17134.590) or of Java 8(1.8.0_171-b11 for me), but it is correct now: os.name gives me Windows 10.
Besides, if you don't trust it, you can check os.version. I have 10.0.
(By the way, I see os.arch:amd64. This is of JVM, not of OS. )

You could also use the .contains() method and just check for the "windows"
string maybe along the lines of
if (System.getProperty("os.name").toLowerCase().contains("windows") && System.getProperty("os.name").toLowerCase().contains(windows version here [xp, 7, 8, etc]))){}
If you need the windows version you could check for all versions and then assume 8.1 or 10 to move around the bug.
if (System.getProperty("os.name").toLowerCase().contains("windows") && System.getProperty("os.name").toLowerCase().contains("xp")){
//code for windows xp }
else if (System.getProperty("os.name").toLowerCase().contains("windows") && System.getProperty("os.name").toLowerCase().contains("vista")){
//code for windows vista
else if (System.getProperty("os.name").toLowerCase().contains("windows") && System.getProperty("os.name").toLowerCase().contains("7")){
//code for windows 7}
else if (System.getProperty("os.name").toLowerCase().contains("windows") && System.getProperty("os.name").toLowerCase().contains("8")){
//code for windows 8}
else if (System.getProperty("os.name").toLowerCase().contains("windows") && System.getProperty("os.name").toLowerCase().contains("8.1")){
//code for both windows 8.1 and 10
}
Now to explain what is going on here:
the if statement is just a conditional to determine the version of windows
The System.getProperty("os.name") returns the name of the os as a string
The .toLowerCase() method makes that returned String lower case
The .contains(String) method checks if the given input string is contained in the String it is being called on
The last statement allows for different code for each os except 8.1 & 10 which would need to be handled as one block :(

How do I get the local hostname if unresolvable through DNS in Java?

This sounds like something that should have been asked before, and it has sort of, but I'm looking to get the local hostname and IP addresses of a machine even when it is not resolvable through DNS (in Java).
I can get the local IP addresses without resolution by iterating through NetworkInterfaces.getNetworkInterfaces().
Any answers to this question I've found indicate to use getLocalHost()
InetAddress localhost = java.net.InetAddress.getLocalHost();
hostName = localhost.getHostName();
but this throws an UnknownHostException if the hostname isn't resolvable through DNS.
Is there no way to get the local hostname without a DNS lookup happening behind the scenes?
edit: the IP address retrieved is 10.4.168.23
The exception is java.net.UnknownHostException: cms1.companyname.com: cms1.companyname.com (hostname changed for pseudo-anonymity), and the hosts file does not contain the hostname. But it does know its hostname, so I'm not sure why I can't get it without an exception being thrown.

Yes, there should be a way in Java to get the hostname without resorting to name service lookups but unfortunately there isn't.
However, you can do something like this:
if (System.getProperty("os.name").startsWith("Windows")) {
// Windows will always set the 'COMPUTERNAME' variable
return System.getenv("COMPUTERNAME");
} else {
// If it is not Windows then it is most likely a Unix-like operating system
// such as Solaris, AIX, HP-UX, Linux or MacOS.
// Most modern shells (such as Bash or derivatives) sets the
// HOSTNAME variable so lets try that first.
String hostname = System.getenv("HOSTNAME");
if (hostname != null) {
return hostname;
} else {
// If the above returns null *and* the OS is Unix-like
// then you can try an exec() and read the output from the
// 'hostname' command which exist on all types of Unix/Linux.
// If you are an OS other than Unix/Linux then you would have
// to do something else. For example on OpenVMS you would find
// it like this from the shell: F$GETSYI("NODENAME")
// which you would probably also have to find from within Java
// via an exec() call.
// If you are on zOS then who knows ??
// etc, etc
}
}
and that will get you 100% what you want on the traditional Sun JDK platforms (Windows, Solaris, Linux) but becomes less easy if your OS is more excotic (from a Java perspective). See the comments in the code example.
I wish there was a better way.

This question is old, but unfortunately still relevant since it's still not trivial to get a machine's host name in Java. Here's my solution with some test runs on different systems:
public static void main(String[] args) throws IOException {
String OS = System.getProperty("os.name").toLowerCase();
if (OS.indexOf("win") >= 0) {
System.out.println("Windows computer name throguh env:\"" + System.getenv("COMPUTERNAME") + "\"");
System.out.println("Windows computer name through exec:\"" + execReadToString("hostname") + "\"");
} else {
if (OS.indexOf("nix") >= 0 || OS.indexOf("nux") >= 0) {
System.out.println("Linux computer name throguh env:\"" + System.getenv("HOSTNAME") + "\"");
System.out.println("Linux computer name through exec:\"" + execReadToString("hostname") + "\"");
System.out.println("Linux computer name through /etc/hostname:\"" + execReadToString("cat /etc/hostname") + "\"");
}
}
}
public static String execReadToString(String execCommand) throws IOException {
Process proc = Runtime.getRuntime().exec(execCommand);
try (InputStream stream = proc.getInputStream()) {
try (Scanner s = new Scanner(stream).useDelimiter("\\A")) {
return s.hasNext() ? s.next() : "";
}
}
}
Results for different operating systems:
OpenSuse 13.1
Linux computer name throguh env:"machinename"
Linux computer name through exec:"machinename
"
Linux computer name through /etc/hostname:""
Ubuntu 14.04 LTS
This one is kinda strange since echo $HOSTNAME returns the correct hostname, but System.getenv("HOSTNAME") does not (this however might be an issue with my environment only):
Linux computer name throguh env:"null"
Linux computer name through exec:"machinename
"
Linux computer name through /etc/hostname:"machinename
"
Windows 7
Windows computer name throguh env:"MACHINENAME"
Windows computer name through exec:"machinename
"
The machine names have been replaced for (some) anonymization, but I've kept the capitalization and structure. Note the extra newline when executing hostname, you might have to take it into account in some cases.

Alternatively, use JNA to call the gethostname function on unixes, avoiding the reverse DNS lookup.
Some notes: on Linux, I believe gethostname simply calls uname and parses the output. On OS X the situation is more complex, as your hostname can be affected by DNS, but those side-effects aside, it's definitely what I get from hostname.
import com.sun.jna.LastErrorException
import com.sun.jna.Library
import com.sun.jna.Native
...
private static final C c = (C) Native.loadLibrary("c", C.class);
private static interface C extends Library {
public int gethostname(byte[] name, int size_t) throws LastErrorException;
}
public String getHostName() {
byte[] hostname = new byte[256];
c.gethostname(hostname, hostname.length)
return Native.toString(hostname)
}
jna-platform.jar includes Win32 functions, so there it's as simple as a call to Kernel32Util.getComputerName().

If you are getting 127.0.0.1 as the IP address then you may need to locate your Operating System specific hosts file and add a mapping to your hostname in it.

This is a bit of a hack. But you could launch a new Process from Java and run the hostname command. Reading the outputstream of the child process would give you the name of the localhost.

Java will read the /etc/hosts file if there is no DNS configured, or rather the corresponding C functions will.

on Linux read
/proc/sys/kernel/hostname

If you're not against using an external dependency from maven central, I wrote gethostname4j to solve this problem for myself. It just uses JNA to call libc's gethostname function (or gets the ComputerName on Windows) and returns it to you as a string.
https://github.com/mattsheppard/gethostname4j
(I think it's almost exactly what #danny-thomas proposed, but maybe more convenient if you're already using Maven ;)

How do I launch a completely independent process from a Java program?

I am working on a program written in Java which, for some actions, launches external programs using user-configured command lines. Currently it uses Runtime.exec() and does not retain the Process reference (the launched programs are either a text editor or archive utility, so no need for the system in/out/err streams).
There is a minor problem with this though, in that when the Java program exits, it doesn't really quit until all the launched programs are exited.
I would greatly prefer it if the launched programs were completely independent of the JVM which launched them.
The target operating system is multiple, with Windows, Linux and Mac being the minimum, but any GUI system with a JVM is really what is desired (hence the user configurability of the actual command lines).
Does anyone know how to make the launched program execute completely independently of the JVM?
Edit in response to a comment
The launch code is as follows. The code may launch an editor positioned at a specific line and column, or it may launch an archive viewer. Quoted values in the configured command line are treated as ECMA-262 encoded, and are decoded and the quotes stripped to form the desired exec parameter.
The launch occurs on the EDT.
static Throwable launch(String cmd, File fil, int lin, int col) throws Throwable {
String frs[][]={
{ "$FILE$" ,fil.getAbsolutePath().replace('\\','/') },
{ "$LINE$" ,(lin>0 ? Integer.toString(lin) : "") },
{ "$COLUMN$",(col>0 ? Integer.toString(col) : "") },
};
String[] arr; // array of parsed tokens (exec(cmd) does not handle quoted values)
cmd=TextUtil.replace(cmd,frs,true,"$$","$");
arr=(String[])ArrayUtil.removeNulls(TextUtil.stringComponents(cmd,' ',-1,true,true,true));
for(int xa=0; xa<arr.length; xa++) {
if(TextUtil.isQuoted(arr[xa],true)) {
arr[xa]=TextDecode.ecma262(TextUtil.stripQuotes(arr[xa]));
}
}
log.println("Launching: "+cmd);
Runtime.getRuntime().exec(arr);
return null;
}
This appears to be happening only when the program is launched from my IDE. I am closing this question since the problem exists only in my development environment; it is not a problem in production. From the test program in one of the answers, and further testing I have conducted I am satisfied that it is not a problem that will be seen by any user of the program on any platform.

There is a parent child relation between your processes and you have to break that.
For Windows you can try:
Runtime.getRuntime().exec("cmd /c start editor.exe");
For Linux the process seem to run detached anyway, no nohup necessary.
I tried it with gvim, midori and acroread.
import java.io.IOException;
public class Exec {
public static void main(String[] args) {
try {
Runtime.getRuntime().exec("/usr/bin/acroread");
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Finished");
}
}
I think it is not possible to to it with Runtime.exec in a platform independent way.
for POSIX-Compatible system:
Runtime.getRuntime().exec(new String[]{"/bin/sh", "-c", "your command"}).waitFor();

I have some observations that may help other people facing similar issue.
When you use Runtime.getRuntime().exec() and then you ignore the java.lang.Process handle you get back (like in the code from original poster), there is a chance that the launched process may hang.
I have faced this issue in Windows environment and traced the problem to the stdout and stderr streams. If the launched application is writing to these streams, and the buffer for these stream fills up then the launched application may appear to hang when it tries to write to the streams. The solutions are:
Capture the Process handle and empty out the streams continually - but if you want to terminate the java application right after launching the process then this is not a feasible solution
Execute the process call as cmd /c <<process>> (this is only for Windows environment).
Suffix the process command and redirect the stdout and stderr streams to nul using 'command > nul 2>&1'

It may help if you post a test section of minimal code needed to reproduce the problem. I tested the following code on Windows and a Linux system.
public class Main {
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws Exception {
Runtime.getRuntime().exec(args[0]);
}
}
And tested with the following on Linux:
java -jar JustForTesting.jar /home/monceaux/Desktop/__TMP/test.sh
where test.sh looks like:
#!/bin/bash
ping -i 20 localhost
as well as this on Linux:
java -jar JustForTesting.jar gedit
And tested this on Windows:
java -jar JustForTesting.jar notepad.exe
All of these launched their intended programs, but the Java application had no problems exiting. I have the following versions of Sun's JVM as reported by java -version :
Windows: 1.6.0_13-b03
Linux: 1.6.0_10-b33
I have not had a chance to test on my Mac yet. Perhaps there is some interaction occuring with other code in your project that may not be clear. You may want to try this test app and see what the results are.

You want to launch the program in the background, and separate it from the parent. I'd consider nohup(1).

I suspect this would require a actual process fork. Basically, the C equivalent of what you want is:
pid_t id = fork();
if(id == 0)
system(command_line);
The problem is you can't do a fork() in pure Java. What I would do is:
Thread t = new Thread(new Runnable()
{
public void run()
{
try
{
Runtime.getRuntime().exec(command);
}
catch(IOException e)
{
// Handle error.
e.printStackTrace();
}
}
});
t.start();
That way the JVM still won't exit, but no GUI and only a limited memory footprint will remain.

I tried everything mentioned here but without success. Main parent Java process can't quit until the quit of subthread even with cmd /c start and redirecting streams tu nul.
Only one reliable solution for me is this:
try {
Runtime.getRuntime().exec("psexec -i cmd /c start cmd.cmd");
}
catch (Exception e) {
// handle it
}
I know that this is not clear, but this small utility from SysInternals is very helpful and proven. Here is the link.

One way I can think of is to use Runtime.addShutdownHook to register a thread that kills off all the processes (you'd need to retain the process objects somewhere of course).
The shutdown hook is only called when the JVM exits so it should work fine.
A little bit of a hack but effective.