Using ProcessBuilder to find version of Java

Question

I am trying to use Java to find out the versions of Java installed on a machine. I have:

List<String> commands = new ArrayList<String>();
commands.add("java.exe");
commands.add("-version");
ProcessBuilder pb = new ProcessBuilder(commands);
pb.directory(new File("C:\\Program Files\\Java\\jdk1.6.0_45\\bin"));
Process p = pb.start();
BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));

while ((s = stdInput.readLine()) != null) {
    System.out.println(s);
}

However, when this is run, the while loop is never executed as the stdInput is empty. If I take out the commands.add("-version"), it will get the input that is output when running "java.exe" command on command line, so it seems adding the -version arguement is causing issues and this also indicates that the directory and java.exe commands are correct. Any help would be appreciated.

Does this question help?

goncalotomas
– goncalotomas

2015-06-03 18:53:42 +00:00
Commented Jun 3, 2015 at 18:53 — goncalotomas
– goncalotomas, Commented Jun 3, 2015 at 18:53
Nope, refer to @Copeg question

Matt Jones
– Matt Jones

2015-06-03 18:54:47 +00:00
Commented Jun 3, 2015 at 18:54 — Matt Jones
– Matt Jones, Commented Jun 3, 2015 at 18:54

copeg · Accepted Answer · 2015-06-03 19:00:57Z

7

The output of java -version is sent to the error stream - reading from that stream should result in the proper output:

BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getErrorStream()));

Alternatively, you can call redirectErrorStream(true) to merge the Input and Error streams. If you just wish to just print to the command line, you can use inheritIO on the ProcessBuilder.

The currently running java version can be found without the need for a ProcessBuilder by retrieving the appropriate System property

System.out.println(System.getProperty("java.version"));

edited Jun 3, 2015 at 19:00

answered Jun 3, 2015 at 18:52

copeg

8,35821 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Matt Jones Over a year ago

I am writing something that gets all versions of Java installed on machines, so I cannot use this method. I need to recursively look in well known locations and run "java.exe -version"

Matt Jones Over a year ago

Ahh there it is, thank you... why would that be sent to error stream??

K Erlandsson · Accepted Answer · 2015-06-03 19:00:21Z

1

java -version prints to stderr. Try using:

ProcessBuilder pb = new ProcessBuilder(commands).redirectErrorStream(true);

That will put stderr in the same stream as stdout and the rest of your code can look as it does now.

answered Jun 3, 2015 at 19:00

K Erlandsson

13.7k6 gold badges53 silver badges67 bronze badges

Collectives™ on Stack Overflow

Using ProcessBuilder to find version of Java

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related