Joining a thread / process in Java after some time - Java

Question

I have the following method, which executes a command as a process and returns the ouput:

public String execute(String command) {
        StringBuffer output = new StringBuffer();
        Process p;
        try {
            p = Runtime.getRuntime().exec(command);
            BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
            String line = "";
            while ((line = reader.readLine()) != null) {
                output.append(line + "\n");
            }
        } catch (Exception e) {
            logger.error(e.getMessage());
        }
        return output.toString();
    }

This code is great whenever the command returns, however for continuing running processes such as top this may never return. The code does not need to keep running continuously. It only needs to capture a snapshot, or it could time out after some time, such as 3 seconds. How can I accomplish that?

Answer 1

Process has a method waitFor. It can be used to force a timeout. For example:

if ((p = Runtime.getRuntime().exec(execPath)) != null) && !p.waitFor(TIMEOUT_CONSTANT, TimeUnit.SECONDS)) {
    p.destroyForcibly();
}