[Java] 外部プロセスの出力をスレッドを使用せずに吸い出す

CommandExecNoThread.java

/*
 * 下記プログラムのスレッド非使用版。
 * https://gist.github.com/froop/b09dd1b687599e0cb1031f3fb6ce0fe2
 */
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;

class StreamPoller {
  InputStream is;
  PrintStream os;
  boolean terminated;

  StreamPoller(InputStream is, PrintStream os) {
    this.is = is;
    this.os = os;
  }

  public void poll() throws IOException {
    if (this.terminated) {
      return;
    }
    StringBuilder buf = new StringBuilder();
    while (is.available() > 0) {
      char c;
      if ((c = (char) is.read()) == -1) {
        os.print(buf.toString());
        this.terminated = true;
        return;
      }
      buf.append(c);
      if (c == '\n') {
        os.print(buf.toString());
        buf = new StringBuilder();
      }
    }
  }
}

public class CommandExecNoThread {
  private static final int POLLING_INTERVAL = 100; // millisec

  public static void main(String[] args) throws IOException, InterruptedException {
    Process proc = Runtime.getRuntime().exec(args[0]);
    StreamPoller errPoller = new StreamPoller(proc.getErrorStream(), System.err);
    StreamPoller outPoller = new StreamPoller(proc.getInputStream(), System.out);

    while (proc.isAlive()) {
      errPoller.poll();
      outPoller.poll();
      Thread.sleep(POLLING_INTERVAL);
    }
    errPoller.poll();
    outPoller.poll();

    System.exit(proc.exitValue());
  }
}