如果先决条件尚未完成处理，如何让线程等待并在先决条件完成后恢复？

Question

我是 Java 多线程的新手。我想执行一个流程执行程序。每个进程包含零到多个先决条件（进程字符串列表）

我的目标是运行一件一件地处理。如果当前线程先决条件尚未完成，它将等待并在其所有先决条件过程完成执行后恢复。

我不确定这是否可行。希望您能够帮助我。请帮助我让它更简单易懂。

我当前的程序输出是：线程开始备份线程启动传输报告线程启动存档报告线程工作备份线程等待传输报告线程等待存档报告线程完成备份添加备份到完成的过程。

我的预期输出：线程开始备份线程启动传输报告线程启动存档报告线程工作备份线程等待传输报告线程等待存档报告线程完成备份添加备份到完成的过程。线程作品传输报告线程完成传输报告将传输报告添加到完成的流程。线程作品存档报告线程完成存档报告将存档报告添加到完成的过程。 == 结束 ==

以下是我当前的代码：

主要应用程序

public class ThreadApp {

    public static void main(String[] args) {
        List<EODProcess> eodProcesses = new ArrayList<>();
        eodProcesses.add(new EODProcess("Back Up", new ArrayList<String>()));
        eodProcesses.add(new EODProcess("Archive Report", Arrays.asList("Transfer Report")));
        eodProcesses.add(new EODProcess("Transfer Report", Arrays.asList("Back Up")));
        
        int count = eodProcesses.size();
        CountDownLatch latch = new CountDownLatch(count);
        CyclicBarrier barrier = new CyclicBarrier(count);
        ExecutorService pool = Executors.newFixedThreadPool(count);

        List<String> finishedProcess = new ArrayList<>();
        
        for (EODProcess eodProcess : eodProcesses) {
            pool.execute(() -> {
                try {
                    System.out.println("Thread starts " + eodProcess.getProcess());
                    Thread.sleep(1000);
                    
                    // Wait IF
                    // Process Prerequisite is not empty
                    // Process Prerequisite is not yet finished
                    while(!eodProcess.getPrerequisites().isEmpty() ||
                            !finishedProcess.containsAll(eodProcess.getPrerequisites())) {
                        System.out.println("Thread waits " + eodProcess.getProcess());
                        barrier.await();
                    }
                    
                    System.out.println("Thread works " + eodProcess.getProcess());
                    Thread.sleep(1000);
                    System.out.println("Thread finished " + eodProcess.getProcess());
                
                    System.out.println("Adding " + eodProcess.getProcess() + " to finished process.");
                    finishedProcess.add(eodProcess.getProcess());
                    
                } catch (Exception e) {
                    System.err.println("Worker thread inrerrupted " + eodProcess.getProcess());
                } finally {
                    latch.countDown();
                }
            });
        }

        try {
            // wait for the threads to be done
            latch.await();
            System.out.println("== End == ");
        } catch (InterruptedException e) {
            System.err.println("Starting interrupted");
        }
        pool.shutdown();
    }

}

EODProcess 对象

public class EODProcess {

    private String process;
    
    private List<String> prerequisites = new ArrayList<>();
    
    public EODProcess(String process, List<String> prerequisites) {
        this.process = process;
        this.prerequisites.addAll(prerequisites);
    }

    public String getProcess() {
        return process;
    }

    public void setProcess(String process) {
        this.process = process;
    }

    public List<String> getPrerequisites() {
        return prerequisites;
    }

    public void setPrerequisites(List<String> prerequisites) {
        this.prerequisites = prerequisites;
    }

}

Answer 1

我简化了我的实现。在我的可调用对象中，我做了这些。

@Override
public String call() throws Exception {
    while (!ThreadApp.finishedProcess.containsAll(eodProcess.getPrerequisites())) {
        System.out.println(eodProcess.getProcess() + " still waiting for prerequisites...");
        Thread.sleep(3000);
    }
    System.out.println(eodProcess.getProcess() + " working...");
    System.out.println(eodProcess.getProcess() + " done!");
    ThreadApp.finishedProcess.add(eodProcess.getProcess());
    return eodProcess.getProcess();
}

谢谢大家的帮助！

如果先决条件尚未完成处理，如何让线程等待并在先决条件完成后恢复？

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