ConcurrentSkipListMap firstKey()抛出NoSuchElementException，即使它

Question

我编写了一个小应用程序，从web套接字接收数据，我将其存储在静态ConcurrentSkipListMap中。应用程序最初创建一个新线程，它在循环调用ConcurrentSkipListMap.firstKey()时无限运行。过了一会儿，即使ConcurrentSkipListMap包含数据，这个调用也会抛出NoSuchElementException。捕获块中的断点我的应用程序示例:

我有一个包含websocket实现和NavigableMap init的缓存类:

package solvethat.net.triobot.Example;
import com.binance.api.client.BinanceApiCallback;
import com.binance.api.client.BinanceApiClientFactory;
import com.binance.api.client.domain.event.DepthEvent;
import com.binance.api.client.domain.market.OrderBook;
import com.binance.api.client.domain.market.OrderBookEntry;
import java.math.BigDecimal;
import java.util.Comparator;
import java.util.List;
import java.util.NavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;
public class AskCacher {
private long updateId;
private final BinanceApiClientFactory factory;
public AskCacher() {
factory = BinanceApiClientFactory.newInstance();
initAsks();
runWebsocket();
}
/**
* Init data getting order book snapshot
*/
private void initAsks() {
try {
OrderBook orderBook = factory.newRestClient().getOrderBook("btcusdt".toUpperCase(), 10);
updateId = orderBook.getLastUpdateId();
NavigableMap<Double, Double> asks = new ConcurrentSkipListMap<>(Comparator.naturalOrder());
for (OrderBookEntry ask : orderBook.getAsks()) {
asks.put(Double.parseDouble(ask.getPrice()), Double.parseDouble(ask.getQty()));
}
StaticData.ask = asks;
} catch (Exception e) {
System.err.println(e.getMessage());
}
}
private void runWebsocket() {
factory.newWebSocketClient().onDepthEvent("btcusdt", new BinanceApiCallback<>() {
/**
* Set ask price and call analysis method
*/
@Override
public void onResponse(DepthEvent depthEvent) {
if (depthEvent.getFinalUpdateId() > updateId) {
updateId = depthEvent.getFinalUpdateId();
updateOrderBook(depthEvent.getAsks());
}
}
/**
* Just print err message
*/
@Override
public void onFailure(final Throwable cause) {
System.err.println(cause.getMessage());
}
});
}
/**
* Updates an order book (asks) with a delta received from the server.
* Whenever the qty specified is ZERO, it means the price should was removed from the order book.
*/
private void updateOrderBook(List<OrderBookEntry> orderBookDeltas) {
for (OrderBookEntry orderBookDelta : orderBookDeltas) {
Double price = Double.parseDouble(orderBookDelta.getPrice());
BigDecimal qty = new BigDecimal(orderBookDelta.getQty());
if (qty.compareTo(BigDecimal.ZERO) == 0) {
// qty=0 means remove this level
StaticData.ask.remove(price);
} else {
StaticData.ask.put(price, Double.parseDouble(orderBookDelta.getQty()));
}
}
// Print best ask to see if cacher is alive
System.out.println("btc-usdt best ask: " + StaticData.ask.firstKey());
// Edit map length
if (StaticData.ask.size() > 10) {
StaticData.ask.tailMap((Double) StaticData.ask.keySet().toArray()[10], true).clear();
}
}}

然后无限循环:

package solvethat.net.triobot.Example;
public class InfiniteLoop {
public void loopProcess() {
Analyzer analyzer = new Analyzer();
while (true) {
analyzer.analyze(StaticData.ask.firstEntry());
}
}}

和分析器类:

package solvethat.net.triobot.Example;
import java.util.Map;
public class Analyzer {
public void analyze(Map.Entry<Double, Double> entry) {
StaticData.AnalyzeObject analyzeObject = new StaticData.AnalyzeObject();
analyzeObject.setBestAsk(entry.getKey());
if (analyzeObject.getBestAsk() > 50000) {
System.out.println("It is a good price!!");
}
}
}

静态数据模型:

package solvethat.net.triobot.Example;
import java.util.NavigableMap;
public class StaticData {
public static NavigableMap<Double, Double> ask;
public static class AnalyzeObject {
double bestAsk;
public double getBestAsk() {
return bestAsk;
}
public void setBestAsk(double bestAsk) {
this.bestAsk = bestAsk;
}
}
}

主类例如:run:

package solvethat.net.triobot.Example;
public class Main {
public static void main(String[] arguments) {
new AskCacher();
new Thread(new InfiniteLoop()::loopProcess).start();
}
}

这个例子只显示了应用程序是如何组成的，但是我不能用它来引发错误，但是我把我的repo打开为public:https://github.com/Sick-E/TrioBot

有谁能帮帮我吗?谢谢你！托马斯

Answer 1

你可以用类似的东西替换你的代码(不需要异常处理)

Optional.ofNullable(trio.getThirdPair().getBids().firstEntry())
.map(Map.Entry::getKey)
.ifPresent(trio.getTrioAnalysis()::setBidThird);