The right way to kill a process in Java

Question

What's the best way to kill a process in Java ?

Get the PID and then killing it with Runtime.exec() ?

Use destroyForcibly() ?

What's the difference between these two methods, and is there any others solutions ?

Solution 1

If the process you want to kill has been started by your application

Then you probably have a reference to it (ProcessBuilder.start() or Runtime.exec() both return a reference). In this case, you can simply call p.destroy(). I think this is the cleanest way (but be careful: sub-processes started by p may stay alive, check Process.destroy does not kill multiple child processes for more info).

The destroyForcibly should only be used if destroy() failed after a certain timeout. In a nutshell

1. terminate process with destroy()
2. allow process to exit gracefully with reasonable timeout
3. kill it with destroyForcibly() if process is still alive

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If the process you want to kill is external

Then you don't have much choice: you need to pass through the OS API (Runtime.exec). On Windows, the program to call will be taskkill.exe, while on Mac and Linux you can try kill.

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Have a look at Support for Process.destroyForcibly() and .isAlive() from Java 8 and Killing a process using Java and Code a Simple Java App to Kill Any Process After a Specified Time for more info.

Solution 2

If you're trying to kill the main process your java code started, I'd suggest using System.exit(). The benefits are explained here: when should we call system exit in java.

Essentially, System.exit() will run shutdown hooks that will make sure any dependent non-daemon processes that may not have completed their work are killed before your process is killed. This is the clean way to do it.

If the process is not yours, you will have to rely on the Operating System to do this work for you as explained in this answer: Killing a Process Using Java

In that case your suggestion of Runtime.exec() a kill on *nix would be a decent way to go.

Now as for destroyForcibly(), you're typically going to call that on a child process spawned by your java code that was presumably started with the process api's ProcessBuilder.start() or Runtime.exec()

Solution 3

the one that worked for me is System.exit(0); it's work's well because it closes all still running processes and components

Comments

[Kariamoss]

Thanks a lot for the explanations ! This is definitely what I was looking for

[v8-E]

Some explanation would greatly improve the quality of the answer and help other users who may encounter similar problems in the future Please take some time to read the help page stackoverflow.com/help/how-to-answer

[31piy]

While this code snippet may solve the question, including an explanation really helps to improve the quality of your post. Remember that you are answering the question for readers in the future, and those people might not know the reasons for your code suggestion.

[hmijail]

If you dig a bit deeper, you might find that actually there is a subclass implementing destroyForcibly() in a different way. For Unices, looks like it's been so since Java 1.5 (look for ProcessImpl, which actually ends up calling native code). So it is not equivalent to a plain destroy().

[android developer]

Why is there "destroyForcibly" anyway, if it's the same? Is there any JVM that it's not the same?

[Jonathan J. Pecany]

Got a question, let's say I need to create a new Runtime.exec() reference to an already started one. How would I do that. Which I need to do for destroying it?