java–在线程中运行时在不同时间获得不同的结果

@Path("/getVersion")
@POST
@Produces(MediaType.APPLICATION_JSON)
public List getVersion(String getVersionJson) throws InterruptedException {
List outputList = new ArrayList();
try {
JSONArray jsOnArr= new JSONArray(getVersionJson);
for (int j = 0; j JSONObject jsOnObj= jsonArr.getJSONObject(j);
String ip = jsonObj.getString("ipaddress");
String username = jsonObj.getString("username");
String password = jsonObj.getString("password");
new Thread() {
public void run() {
//outputList.add(ip);
final String cOnnectionStatus= getSSHConnection(ip, username, password);
// outputList.add(connectionStatus);
if (connectionStatus.equals("Connected")) {
// outputList.add(connectionStatus);
//Version Check
expect.send("bwshowver" + "\n");
if (expect.expect("$") > -1) {
String cOntt= "";
cOntt= (expect.before);
if (contt != null && contt != "") {
cOntt= contt.replaceAll("\n+", "\n");
cOntt= contt.replaceAll(" +", " ");
String splitter[] = contt.split("\n");
for (int i = 0; i if (splitter[i].contains("Patches")) {
final String patches = splitter[i];
}
//version
if (splitter[i].contains("version")) {
// final String version = splitter[i];
outputList.add(splitter[i]);
}
}
} else {
final String v1 = "Error in version check";
System.out.println("Error in version check");
}
}
} else {
outputList.add(connectionStatus);
}
}
}.start();
}
} catch (Exception e) {
final String v = "Error";
// logger.error("Exception in getVersion Function-ServService Class: " + e.getMessage());
} finally {
stopSSH();
}
Thread.sleep(20000);
//outputList.add("ffk");
// outputList.add("f");
return outputList;
}


我已经使用Threads创建了一个方法.在这个方法中,我发送一个由json对象组成的jsonarray.以前我创建了这个方法没有线程,它正常工作.现在将它改成线程后,我在不同的时间得到不同的结果.你能告诉我哪里出错了吗？

解决方法:

您可以在上面的代码中改进3件主要内容：

>从多个线程修改线程安全集合时使用它们.如果集合没有明确提到它是线程安全的,那么您需要自己获取锁定或切换到线程安全的集合
>使用Thread.sleep()进行同步通常是个坏主意.您应该使用更精确的同步方法来避免不稳定的行为.我选择在这里使用CountDownLatch,你可以使用其他同步工具.
>在线程内部抛出的异常不会传播到主线程,但可能只是在该线程内部冒出来并且永远不会被注意到.您希望能够注意到runnable中抛出的异常并在最后处理它.我还将修改代码,向您展示如何处理异常的粗略指南.

要以简单的格式回答您的问题,您可以希望对代码进行调整：

public List getVersion(String getVersionJson)
throws InterruptedException, IOException {
// You must use a thread-safe list.
final List outputList = Collections.synchronizedList(new ArrayList());
// This reference is used to keep track of exceptions thrown
// in the runnable.
final AtomicReference exceptiOnReference=
new AtomicReference(null);
// This latch acts as a synchronization barrier so that all threads
// must have put data into outputList before the code will go
// past the latch.await() call
final CountDownLatch latch = new CountDownLatch(jsonArr.length());
for (int j = 0; j new Thread() {
public void run() {
try {
// Do network I/O stuff
outputList.add(resultFromNetworkStuff);
latch.countDown();
} catch (IOException e) {
// Set the exception for later retrieval
exceptionReference.compareAndSet(null, e);
}
}
}.start();
}
// Wait for all the threads to finish before continuing.
try {
latch.await();
} finally {
// Even if we're interrupted, we want to close the connection.
closeSSH();
}
if (exceptionRef.get() != null) {
// Throw any exceptions we see in our threads.
throw exceptionRef.get();
}
return outputList;
}