我有一个多线程Java程序，它会导致内存一致性错误。我天真地试图通过声明我的所有变量volatile和方法同步来解决问题，但这没有奏效。
有时，上一个对象的内存会显示在其他新对象中。这是现实世界的输出：
<Thread-13> OptionRow (AMGN_062714P116) expDate set to 2014-06-27
Thread-9 2) OFT-Thread (AIG_052314C50) populateTable expDate = 2014-06-27 year=2014 month=5 day=23
<Thread-9> OptionRow (AIG_052314C50) expDate set to 2014-05-23
您可以看到Thread 9将expDate设置为Thread 13设置该值的相同值。这是错误的，不知何故，正确的价值赶上了。很难将它变成一个小代码片段，所以我会尽量准确地描述代码序列，同时保持简短。
编辑：我修改了每个请求的代码（原始代码太短）
此代码中仍然缺少一些东西。我不能包含它，因为它允许您连接到TDAmeritrade的API服务器。我可以创建随机生成的日期，如果这会更好？我知道这不会为你编译。我还在学习这个网站的协议。如果这是错误的，请告诉我。
另外，当我将它作为单个线程运行时，它起作用了。没有内存错误。所以，它绝对是多线程的。这个版本与我最初发布的版本不同。我希望使用ExecutorService线程池会有所帮助。它没有帮助。
import java.util.Iterator;
import java.util.TreeSet;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import broker.Root;
import java.util.ArrayList;
import java.util.GregorianCalendar;
import networking.ParseBinaryOptionChain;
public class StackOverflowCode {
public StackOverflowCode () {
Root root = new Root();
MyStatement myStatement = new MyStatement (root);
root.setStatement(myStatement);
networking.TDAConnection tdaConn = new networking.TDAConnection(root);
tdaConn.login();
root.setTDAConnection(tdaConn);
Table table = new Table(root);
new Thread(table).start();
}
public static void main(String[] args){
new StackOverflowCode();
}
}
class Table implements Runnable {
Root root;
private ArrayList <OptionRow> optionList;
public Table(Root r){
// guess initial list size is 125,000 symbols
optionList = new ArrayList<>(125000);
root = r;
}
@Override
public void run() {
getUnderlyingList();
}
public void addAll(ArrayList options) {
optionList.addAll(options);
}
private void getUnderlyingList() {
try {
final TreeSet dbStocks = (TreeSet) root.getMyStatement().getStockSymbolsFromOptionsFilterDatabase();
ExecutorService pool = Executors.newFixedThreadPool(10);
String stock = null;
for (Iterator it = dbStocks.iterator(); it.hasNext(); stock = (String) it.next()) {
pool.submit(new Download(root, stock, this));
}
pool.shutdown();
pool.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
class Download implements Runnable {
private String stock;
private Root root;
private Table parent;
public Download(Root root, String stock, Table parent) {
this.root = root;
this.stock = stock;
this.parent = parent;
}
@Override
public void run() {
PopulateTable pop = new PopulateTable(root, stock, parent);
pop.populateTable();
}
}
class PopulateTable {
private String stockSymbol;
private Root root;
private Table parent;
private ArrayList <OptionRow> optionList;
private ParseBinaryOptionChain pBOC;
private volatile OptionRow option;
private volatile GregorianCalendar expDate;
public PopulateTable(Root root, String stockSymbol, Table parent) {
this.root = root;
this.stockSymbol = stockSymbol;
this.parent = parent;
optionList = new ArrayList<>();
}
public synchronized void populateTable() {
try {
// Download all the options associated with the stock symbol
// and parse them directly from the Internet.
pBOC = root.getTDAConnection().requestBinaryOptionChain(stockSymbol);
root.getMyStatement().setLastStockPrice(stockSymbol, pBOC.getsLast());
root.getMyStatement().setCompanyName(stockSymbol, new networking.YahooConnect(root).symbolLookup(stockSymbol));
// Here's where we will be going through each option. Collect the info
// we are interested in here. Put the info in the options table.
while (pBOC.next()&&root.buttonIsOnline()){
boolean isCall = false;
if (pBOC.getPutCallIndicator()=='C')
isCall = true;
String date = pBOC.getODate();
expDate = new GregorianCalendar (
Integer.parseInt(date.substring(0, 4)),
(Integer.parseInt(date.substring(4, 6))-1),
Integer.parseInt(date.substring(6, 8)));
System.out.println ("<"+Thread.currentThread().getName()+"> ("+pBOC.getOSymbol()+") populateTable expDate = "
+root.getHelp().getSdfYearMonthDay().format(expDate.getTime())
+" year="+Integer.parseInt(date.substring(0, 4))
+" month="+Integer.parseInt(date.substring(4, 6))
+" day="+ Integer.parseInt(date.substring(6, 8)));
System.out.println (Thread.currentThread().getName()+" 2) OFT-Thread ("+pBOC.getOSymbol()+") populateTable expDate = "
+root.getHelp().getSdfYearMonthDay().format(expDate.getTime())
+" year="+Integer.parseInt(date.substring(0, 4))
+" month="+Integer.parseInt(date.substring(4, 6))
+" day="+ Integer.parseInt(date.substring(6, 8)));
option = new OptionRow(root, expDate, new GregorianCalendar());
optionList.add(option);
}
// add all the options to the parent table
parent.addAll(optionList);
// Saves all the downloaded info to the database
root.getMyStatement().insertOptionsInfoForFilter(optionList);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
class OptionRow {
private Root root;
private volatile GregorianCalendar expDate;
public OptionRow (Root root, GregorianCalendar expDate, Object... o) {
this.root = root;
this.expDate = expDate;
}
}
如果有人能告诉我为什么会发生错误以及如何解决错误，我真的很喜欢它吗？
答案 0 :(得分：2)
我认为问题只是Root.getHelp().getSdfYearMonthDay()正在返回共享日期格式化程序。这些对象不是线程安全的，通常，共享这些对象会导致格式化另一个线程的日期。
而不是
root.getHelp().getSdfYearMonthDay()
替换为：
new SimpleDateFormat("yyyy-MM-dd")
看看问题是否仍然存在。我敢打赌它已经消失了。