java - 如何计算我的多线程程序的运行时间

Question

我正在尝试计算我的程序创建的所有线程的总数，但我的代码仅计算调用的时间。

我确信，因为在输出中我看到在所有线程完成之前打印的差异

下面是我的主程序RequestProcessor这里是我的线程类

int i = 0;
List<Customer>customers = customer.getCustomers();
long startTimestamp = System.currentTimeMillis();
for (Customer c: customers){
    new RequestProcessor(c, i).start();
    i++;
}
long endTimestamp = System.currentTimeMillis();
System.out.println("difference  = "+(endTimestamp - startTimestamp));

下面是请求处理器类

public RequestProcessor( Customer customer , int threadSeq ) {
    super();
    this.customer = customer;
    this.threadSeq = threadSeq;
}

@Override
public void run() {
    // TODO Auto-generated method stub
    processRequest();
    super.run();
}

public void processRequest(){
    //performing execution on customer here
    System.out.println("processing "+ customer.getName()+" thread seq "+threadSeq);
}

下面是我得到的输出

processing customer9 thread seq 9
processing customer7 thread seq 7
difference  = 4
processing customer3 thread seq 3
processing customer2 thread seq 2

我尝试使用 join 但对我不起作用

Answer 1

您可以使用CountDownLatch 。它是一个重要的并发工具类。如果您想了解更多有关java多线程程序的信息。请参阅实践中的 Java 并发 [Brian Goetz]

这本书

 int i = 0;
  List<Customer>customers = customer.getCustomers();
  CountDownLatch cdl =new CountDownLatch(customers.size());      // new code 
  long startTimestamp = System.currentTimeMillis();

   for (Customer c: customers){
      new RequestProcessor(cdl,c, i).start();
      i++;
    }

   cdl.await();                                                      // new code . 
  // the thread will hang up unitl all RequestProcessor run cdl.countDown() ;
    long endTimestamp = System.currentTimeMillis();
    System.out.println("difference  = "+(endTimestamp - startTimestamp));

RequestProcessor.class

public RequestProcessor(CountDownLatch cdl, Customer customer , int threadSeq ) {
        super();
        this.customer = customer;
        this.threadSeq = threadSeq;
        this.cdl=cdl;                                            // new code 
        }
    @Override
    public void run() {
        // TODO Auto-generated method stub
       processRequest();
       super.run();
       cdl.countDown();                                          // new code 
    }