Swing/SingleThreadExecutor の変更点

---
category: swing
folder: SingleThreadExecutor
title: SwingWorkerを一スレッドずつ順番に実行する
tags: [SwingWorker, ExecutorService, JTable, JProgressBar]
author: aterai
pubdate: 2019-06-10T16:52:22+09:00
description: JTableのセルに配置したJProgressBarを操作するSwingWorkerタスクを一つずつ順番に実行します。
image: https://drive.google.com/uc?id=1x3PqH08NWiKXBFZl355XaqHN5fyc1zEdrg
---
* Summary [#summary]
`JTable`のセルに配置した`JProgressBar`を操作する`SwingWorker`タスクを一つずつ順番に実行します。

#download(https://drive.google.com/uc?id=1x3PqH08NWiKXBFZl355XaqHN5fyc1zEdrg)

* Source Code Examples [#sourcecode]
#code(link){{
ExecutorService executor = Executors.newSingleThreadExecutor();
// ...
protected final void addActionPerformed() {
  int key = model.getRowCount();
  SwingWorker<Integer, Integer> worker = new BackgroundTask() {
    @Override protected void process(List<Integer> c) {
      if (isCancelled()) {
        return;
      }
      if (!isDisplayable()) {
        System.out.println("process: DISPOSE_ON_CLOSE");
        cancel(true);
        executor.shutdown();
        return;
      }
      c.forEach(v -> model.setValueAt(v, key, 2));
    }

   @Override protected void done() {
      if (!isDisplayable()) {
        System.out.println("done: DISPOSE_ON_CLOSE");
        cancel(true);
        executor.shutdown();
        return;
      }
      String text;
      int i = -1;
      if (isCancelled()) {
        text = "Cancelled";
      } else {
        try {
          i = get();
          text = i >= 0 ? "Done" : "Disposed";
        } catch (InterruptedException | ExecutionException ex) {
          text = ex.getMessage();
        }
      }
      System.out.format("%s:%s(%dms)%n", key, text, i);
      // executor.remove(this);
    }
  };
  model.addProgressValue("example", 0, worker);
  executor.execute(worker);
}
}}

* Description [#explanation]
* Description [#description]
上記のサンプルでは、`Executors.newSingleThreadExecutor()`で作成した単一スレッド用の`executor`を使用して順番に一つづ`SwingWorker`を実行しています。

----
- `Executors.newSingleThreadExecutor()`で生成される`ExecutorService`は`Executors.newFixedThreadPool(1)`のものとほぼ同じ
-- [https://stackoverflow.com/questions/21300924/difference-between-executors-newfixedthreadpool1-and-executors-newsinglethread java - Difference between Executors.newFixedThreadPool(1) and Executors.newSingleThreadExecutor() - Stack Overflow]
-- [https://torutk.hatenablog.jp/entry/20130824/p1 Executors.newSingleThreadExecutor()が返すもの - torutkのブログ]

----
- デフォルトの`SwingWorker`は`10`個のワーカ・スレッドを同時に実行可能
-- [https://community.oracle.com/thread/1364600 Swing - Maximum number of SwingWorker objects in a Swing app?]
#code{{
public abstract class SwingWorker<T, V> implements RunnableFuture<T> {
  /**
   * number of worker threads.
   */
  private static final int MAX_WORKER_THREADS = 10;
// ...
executorService =
    new ThreadPoolExecutor(MAX_WORKER_THREADS, MAX_WORKER_THREADS,
                           10L, TimeUnit.MINUTES,
                           new LinkedBlockingQueue<Runnable>(),
                           threadFactory);
}}

* Reference [#reference]
- [https://docs.oracle.com/javase/jp/8/docs/api/java/util/concurrent/Executors.html#newSingleThreadExecutor-- Executors#newSingleThreadExecutor() (Java Platform SE 8)]
- [[JTableのセルにJProgressBarを表示>Swing/TableCellProgressBar]]
- [https://bugs.openjdk.org/browse/JDK-6880336 &#91;JDK-6880336&#93; SwingWorker deadlocks due one thread in the swingworker-pool - Java Bug System]

* Comment [#comment]
#comment
#comment