[Java] 外部プロセスが終了したら、それ以降の標準出力・エラー出力を捨てる

CommandExec.java

/*
 * 外部プロセスが終了したら、それ以降の標準出力・エラー出力を捨てる。
 * 参考: FIO07-J. 外部プロセスに IO バッファをブロックさせない - JPCERT/CC
 * https://www.jpcert.or.jp/java-rules/fio07-j.html
 */
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;

class StreamGobbler extends Thread {
  InputStream is;
  PrintStream os;
  boolean terminated;

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

  public void run() {
    try {
      StringBuilder buf = new StringBuilder();
      while (true) {
        while (is.available() == 0) {
          if (terminated) {
            return;
          }
          Thread.sleep(100);
        }

        char c;
        if ((c = (char) is.read()) == -1) {
          os.print(buf.toString());
          return;
        }
        buf.append(c);
        if (c == '\n') {
          os.print(buf.toString());
          buf = new StringBuilder();
        }
      }
    } catch (Throwable t) {
      t.printStackTrace();
    } finally {
      try {
        is.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

  void terminate() {
    this.terminated = true;
  }
}

public class CommandExec {
  public static void main(String[] args) throws IOException, InterruptedException {
    Process proc = Runtime.getRuntime().exec(args[0]);
    StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), System.err);
    StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), System.out);

    errorGobbler.start();
    outputGobbler.start();

    int exitVal = proc.waitFor();

    errorGobbler.terminate();
    outputGobbler.terminate();

    errorGobbler.join();
    outputGobbler.join();

    System.exit(exitVal);
  }
}