void onExit(int pid, int exitValue) {
        ProcessReference processReference = null;

        synchronized (processReferences) {
            cleanUp();
            if (pid >= 0) {
                processReference = processReferences.remove(pid);
            } else if (exitValue == WAIT_STATUS_NO_CHILDREN) {
                if (processReferences.isEmpty()) {
                    /**
                     * There are no eligible children; wait for one to be
                     * added. The wait() will return due to the
                     * notifyAll() call below.
                     */
                    try {
                        processReferences.wait();
                    } catch (InterruptedException ex) {
                        // This should never happen.
                        throw new AssertionError("unexpected interrupt");
                    }
                } else {
                    /**
                     * A new child was spawned just before we entered
                     * the synchronized block. We can just fall through
                     * without doing anything special and land back in
                     * the native wait().
                     */
                }
            } else {
                // Something weird is happening; abort!
                throw new AssertionError("unexpected wait() behavior");
            }
        }

        if (processReference != null) {
            ProcessImpl process = processReference.get();
            if (process != null) {
                process.setExitValue(exitValue);
            }
        }
    }//源代码片段来自云代码http://yuncode.net