fix thread command NullPointerException. #2875

core/src/main/java/com/taobao/arthas/core/command/monitor200/ThreadCommand.java

@@ -212,8 +212,10 @@ public class ThreadCommand extends AnnotatedCommand {
         List<BusyThreadInfo> busyThreadInfos = new ArrayList<BusyThreadInfo>(topNThreads.size());
         for (ThreadVO thread : topNThreads) {
             ThreadInfo threadInfo = findThreadInfoById(threadInfos, thread.getId());
-            BusyThreadInfo busyThread = new BusyThreadInfo(thread, threadInfo);
+            if (threadInfo != null) {
-            busyThreadInfos.add(busyThread);
+                BusyThreadInfo busyThread = new BusyThreadInfo(thread, threadInfo);
+                busyThreadInfos.add(busyThread);
+            }
         }
         process.appendResult(new ThreadModel(busyThreadInfos));
         return ExitStatus.success();

core/src/main/java/com/taobao/arthas/core/util/ThreadUtil.java

@@ -266,6 +266,9 @@ abstract public class ThreadUtil {
     }
 
     public static String getFullStacktrace(BusyThreadInfo threadInfo, int lockIdentityHashCode, int blockingThreadCount) {
+        if (threadInfo == null) {
+            return "";
+        }
         StringBuilder sb = new StringBuilder("\"" + threadInfo.getName() + "\"");
         if (threadInfo.getId() > 0) {
             sb.append(" Id=").append(threadInfo.getId());