Java:Threadpoolexecutor - 使用作业列表来提交作业？

Question

下面的代码是一个Customer和jobManager。客户有姓名、地​​址和账户余额。工作是从一个客户到另一个客户的汇款。这是一个 Threadpoolexecutor 训练程序。以下版本有效，我一个一个地提交作业。

客户.java

public class customer {

    private String name;
    private String adress;
    private Double accountBalance;

    public customer(String name, String adress, Double accountBalance)
    {
        this.name = name;
        this.adress = adress;
        this.accountBalance = accountBalance;
    }

    public String getName() { return name; }

    public String getAdress()
    {
        return adress;
    }

    public Double getAccountBalance(){return accountBalance;}

    public void setAccountBalance(double accountBalance){this.accountBalance=accountBalance;}

    @Override
    public String toString(){

        return "[" + name+"; " +adress+"; "+accountBalance+"]";
    }
}

customerOrganizer.java

import java.util.ArrayList;
import java.util.List;

public class customerOrganizer {

    private static final customerOrganizer myJobOrganizer = new customerOrganizer();

    public static customerOrganizer getJobOrganizer(){
        return myJobOrganizer;
    }

    private List<customer> customerList = new ArrayList<customer>();

    public void add_customer(customer kunde)
    {
        this.customerList.add(kunde);
    }

    public Iterable<customer> all_customers()
    {
        return this.customerList;
    }

    public static customerOrganizer getInstance()
    {
        return myJobOrganizer;
    }

}

工作.java

public class job implements Runnable {
    private customer kunde1;
    private customer kunde2;
    private Double transfer;

    public job(customer kunde1, customer kunde2, Double transfer) {
        this.kunde1 = kunde1;
        this.kunde2 = kunde2;
        this.transfer = transfer;
    }

    @Override
    public String toString(){

        return "[" + kunde1+"; " +kunde2+"; "+transfer+"]";
    }

    public void run() {

        System.out.println("Starting transfer");

        Double geber = this.kunde1.getAccountBalance();
        Double nehmer = this.kunde2.getAccountBalance();

        Double geberNeu = geber - this.transfer;
        this.kunde1.setAccountBalance(geberNeu);

        Double nehmerNeu = nehmer + this.transfer;
        this.kunde2.setAccountBalance(nehmerNeu);
        System.out.println("Transfer done");
    }
}

jobOrganizer.java

public class jobOrganizer {

    private static final jobOrganizer myJobOrganizer = new jobOrganizer();

    public static jobOrganizer getMyJobOrganizer() {
        return myJobOrganizer;
    }

    private List<job> jobList = new ArrayList<job>();

    public int getAmount(){ return jobList.size();}

    public void add_job(job newJob) {
        this.jobList.add(newJob);
    }

    public Iterable<job> all_jobs() {
        return this.jobList;
    }

    public static jobOrganizer getInstance() {
        return myJobOrganizer;
    }

主.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Main {

    public static void main(String[] args) {
        customerOrganizer myCustomerOrganizer = new customerOrganizer();
        jobOrganizer myJobOrganizer= new jobOrganizer();

        customer mueller = new customer("Tim Mueller", "Strasse 1", 1077.00);
        customer john = new customer("John Doe", "Strasse 2",503.00);
        customer meier = new customer("John Meier", "Strasse 3", 8500.50);
        customer wurst = new customer("Hans Wurst", "Strasse 4", 1000.00);

        myCustomerOrganizer.add_customer(mueller);
        myCustomerOrganizer.add_customer(john);
        myCustomerOrganizer.add_customer(meier);
        myCustomerOrganizer.add_customer(wurst);

        job transfer1= new job(meier,wurst,500.50);
        job transfer2= new job(mueller,john,77.00);

        myJobOrganizer.add_job(transfer1);
        myJobOrganizer.add_job(transfer2);

        // this works:
        ExecutorService executor = Executors.newFixedThreadPool(2);
        executor.submit(transfer1);
        executor.submit(transfer2);
        executor.shutdown();


    }}

所以，我确实有一个 jobList，而且我有想法，我应该使用它。我不想一个接一个地提交作业，而是根据作业列表提交它们。一开始我想到了这样的事情:

 int threads = myJobOrganizer.getAmount();
        ExecutorService executor = Executors.newFixedThreadPool(threads);
        for (int i = 0; i <threads+1; i++){
            //submit jobs? execute?
        }

此外，myJobOrganizer 需要实现 Runnable 吗？我还看到解决方案是这样的:

for(condition){

        executor.execute(new Runnable() {

            @Override
            public void run() {
              submit the jobs?
                }
            }}

但是我真的不知道，该怎么做。基本上，我缺少如何以正确的方式从我的 jobList 中提取作业，以便我可以将它们提交给执行程序服务>。<

关于线程安全的更新

因此，我点击了 Rab 提供的链接，我使用了 CompletionService。 Main.java 的最后一部分现在看起来像这样:

int threads = myJobOrganizer.getAmount();

System.out.println(myCustomerOrganizer.all_customers().toString());
// executor service   
ExecutorService executor = Executors.newFixedThreadPool(threads);
// completion service is applied on executor
CompletionService service = new ExecutorCompletionService(executor);

for(Callable<Job> myJob : myJobOrganizer.all_jobs()){
    service.submit(myJob);
}
executor.shutdown();
// pause the main for control printout -> not nice yet, I am working on 
// joining threads
try {
    Thread.sleep(1000);
} catch (InterruptedException e) {
    e.printStackTrace();
}
// control print
System.out.println(myCustomerOrganizer.all_customers().toString());

请注意，此编辑旨在完成条目，但仍然是错误的(很遗憾)。提供的答案链接到原始问题，不涉及线程安全

感谢您的时间和努力!

Answer 1

ExecutorService处理如何在 worker 之间分配任务。您所要做的就是将工作一项一项地传递。

for (job jobObj : myJobOrganizer.all_jobs()) 
    executor.submit(jobObj);

注意 sumbit返回 Future<?> ，用于跟踪您的任务是否已完成，或者它们是否出错(以及任务结果，但 runnable 没有结果)。如果你关心这些东西，你会想把它们收集在某种容器中，比如 List .

---

如果您更改 job进入 Callable<Void> ，提交会容易得多。 Callable是 Runnable 的某种扩展，允许任务在完成时产生结果。由于您的转账没有结果，使用java.lang.Void作为通用参数的填充类型就可以了。

现在，只需执行 executor.invokeAll(myJobOrganizer.all_jobs())就足够了。这将节省一些上下文切换，加快速度。 (其实很重要，因为你的任务都很小)

---

顺便说一句，您应该知道并发访问需要适当的同步，而您没有。如果不同的工作涉及同一个帐户，您的帐户最终可能会处于错误状态。我们还通常使用 LargeCamelCase 命名类，使用 smallCamelCase 命名方法。