Java: How to make this main thread wait for the new thread to terminate

Question

I have a java class that creates a process, called child, using ProcessBuilder. The child process generates a lot of output that I am draining on a separate thread to keep the

Answer 1

final StringBuffer outtext = new StringBuffer("");  
Thread outputDrainThread = new Thread(new Runnable() {
    public void run() {
        // ... 
    }
}).start();

// ...

//  ***HERE IS WHERE I NEED TO WAIT FOR THE THREAD TO FINISH ***
outputDrainThread.join();    

// ...
return outtext.toString();