java - Java:Threadpoolexecutor - 使用作业列表提交作业?
问题描述
下面的代码是一个Customer
和jobManager
。客户有姓名、地址和 accountBalance。工作是从一个客户到另一个客户的资金转移。这是一个 Threadpoolexecutor 培训计划。以下版本有效,我一一提交作业。
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+"]";
}
}
客户组织者.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;
}
}
作业.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");
}
}
工作组织者.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 并且我有想法,我应该使用它。我不想一一提交作业,而是根据作业列表提交它们。我一开始就想到了这样的事情:
int threads = myJobOrganizer.getAmount();
ExecutorService executor = Executors.newFixedThreadPool(threads);
for (int i = 0; i <threads+1; i++){
//submit jobs? execute?
}
此外,myJobOrganizer 是否需要实现 Runnable?我还看到解决方案类似于:
for(condition){
executor.execute(new Runnable() {
@Override
public void run() {
submit the jobs?
}
}}
但我真的不知道,该怎么做。基本上,我错过了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 executor service >.<
关于线程安全的更新
所以,我按照 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,此编辑是为了完成条目,但仍然是错误的(遗憾的是)。提供的答案与原始问题相关联,不涉及线程安全
感谢您的时间和精力!
解决方案
ExecutorService
处理如何在工作人员之间分配任务。您所要做的就是一份一份地传递工作。
for (job jobObj : myJobOrganizer.all_jobs())
executor.submit(jobObj);
请注意,sumbit
return aFuture<?>
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)。如果您关心这些东西,您可能希望将它们收集在某种容器中,例如List
.
如果将 更改job
为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。由于您的传输没有结果,因此将java.lang.Void
其用作泛型参数的填充类型就可以了。
现在,只要做executor.invokeAll(myJobOrganizer.all_jobs())
就足够了。这将节省一些上下文切换,加快速度。(实际上非常重要,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。我们也常用 LargeCamelCase 命名类,smallCamelCase 命名方法。
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