等到被调用的jar执行完成

Question

In my Java program, I start an external .jar file which modifies the system clipboard content. After that I continue with the data written to the clipboard. Unfortunately it looks like the jar gets started and the program doesn't wait until the jar execution is finished.

Here is the code I use to start the jar file:

import java.io.IOException;

public class JarExecutor {

    private String pathToJar = "";
    private String jarFile = "";
    private String pathToJava = "C:\\ProgramData\\Oracle\\Java\\javapath\\javaw.exe";

    public JarExecutor(String pathToJar, String jarFile) {
        this.pathToJar = pathToJar;
        this.jarFile = jarFile;
    }

    public void execute() {

        ProcessBuilder pb = new ProcessBuilder(pathToJava, "-jar", pathToJar + jarFile);
        try {
            Process p = pb.start();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

And that's from the main program:

public static void main(String[] args) {
        String pathToJar = "\\\\some\\net\path";
        String jarFile = "externalProgram.jar";

        JarExecutor myExecutor = new JarExecutor(pathToJar, jarFile)
        myExecutor.execute();

        [...]
}

As long as I put a Thread.sleep(ms) with ms > 3000 after the myExecutor.execute() in my program it works, but I guess that's no proper way to wait for the other process to be finished.

Answer 1

Right there in the Process documentation :

waitFor

 public abstract int waitFor() throws InterruptedException 

Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated. This method returns immediately if the subprocess has already terminated. If the subprocess has not yet terminated, the calling thread will be blocked until the subprocess exits.

Answer 2

Using waitFor would be the perfect solution if you need the main to proceed only after the jar execution is done. Otherwise, you will be looking at some sort of interprocess communication. Try using sockets to pass messages between the processes.