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SPL(Structured Process Language) A programming language specially for structured data computing.
There is a newer version: 20241126
package com.scudata.thread;

import java.util.LinkedList;

import com.scudata.dm.Env;

/**
 * ?̳߳ض??????ڶ??̴߳???????
 * ?߳?????????Env.getParallelNum()
 * @author WangXiaoJun
 *
 */
public class ThreadPool{
	private static ThreadPool instance;

	private WorkThread[] threads;
	private LinkedList jobList = new LinkedList();
	private boolean shutdown; // ?Ƿ?ر??߳?

	// ?̳߳??????Ĺ????߳?
	private class WorkThread extends Thread {
		private WorkThread(ThreadGroup group, String name) {
			super(group, name);
		}

		public void run() {
			while (true) {
				// ???????б???ͬ??
				synchronized(jobList) {
					if (shutdown) {
						// ?̳߳ص????˹رգ??????߳?
						return;
					}

					// ???û????????ȴ?
					if (jobList.size() == 0) {
						try {
							jobList.wait();
						} catch (InterruptedException e) {
							if (shutdown) {
								return;
							}
						}
					}
				}

				// ?ѵ?һ??????ȡ????ִ??
				Job job = null;
				synchronized(jobList) {
					if (jobList.size() > 0) {
						job = jobList.removeFirst();
					}
				}

				if (job != null) {
					try {
						job.run();
					} catch (Throwable e) {
						job.setError(e);
					}

					job.finish();
				}
			}
		}
	}

	private ThreadPool(int threadCount) {
		ThreadGroup group = Thread.currentThread().getThreadGroup();
		// ???鲻??ide?????ģ?ide?????ide???????߳???Ľ????̷߳??????˷?????ݹ?????????????߳?????߳?
		/*while (true) {
			ThreadGroup g = group.getParent();
			if (g == null) {
				break;
			} else {
				group = g;
			}
		}*/

		threads = new WorkThread[threadCount];
		for (int i = 0; i < threadCount; ++i) {
			threads[i] = new WorkThread(group, "ThreadPool" + i);
			threads[i].setDaemon(true);
			threads[i].start();
		}
	}

	/**
	 * ȡ???̳߳أ??߳???ΪEnv.getCallxParallelNum()??MAX_THREAD_COUNT?е?С?ߣ????Ҳ?С??2
	 * @return ThreadPool
	 */
	public static synchronized ThreadPool instance() {
		if (instance == null || instance.shutdown) {
			int n = Env.getParallelNum();
			if (n < 2) {
				n = 2;
			}

			instance = new ThreadPool(n);
		} else {
			// ????Ƿ????߳?????
			WorkThread[] threads = instance.threads;
			for (int i = 0, len = threads.length; i < len; ++i) {
				if (!threads[i].isAlive()) {
					threads[i] = instance.new WorkThread(threads[i].getThreadGroup(), "ThreadPool" + i);
					threads[i].setDaemon(true);
					threads[i].start();
				}
			}
		}

		return instance;
	}
	
	/**
	 * ?²???һ???̳߳?
	 * @param threadCount ?߳?????????????????õ????????????????????
	 * @return ThreadPool
	 */
	public static synchronized ThreadPool newInstance(int threadCount) {
		int n = Env.getParallelNum();
		if (threadCount > n) {
			if (n < 1) {
				threadCount = 1;
			} else {
				threadCount = n;
			}
		}
		
		return new ThreadPool(threadCount);
	}

	/**
	 * ?ڵ????Ҫ?ϸ???ִ?У???Ҫ֧??1??????
	 * @param size ?߳???
	 * @return
	 */
	public static synchronized ThreadPool newSpecifiedInstance(int size) {
		int n = size;
		if (n < 1) {
			n = 1;
		}
		
		return new ThreadPool(n);
	}

	/**
	 * ?ر??Ѿ??????̳߳?ʵ???????̳߳?ʵ?????ܼ???ʹ??
	 */
	public synchronized void shutdown() {
		shutdown = true;
		synchronized(jobList) {
			jobList.notifyAll();
			jobList.clear();
		}
	}

	/**
	 * ?ύһ?????????????أ?job.join?ȴ????????
	 * @param job Job
	 */
	public void submit(Job job) {
		job.reset();
		synchronized(jobList) {
			jobList.add(job);
			jobList.notify();
		}
	}
	
	protected void finalize() throws Throwable {
		try {
			if (!shutdown) {
				jobList.notifyAll();
				jobList.clear();
			}
		} catch (Throwable e) {
		}
	}

	/**
	 * ?????̳߳?????߳?????
	 * @return
	 */
	public int getThreadCount() {
		return threads.length;
	}
}