[misc] avoid race condition on Connection.abort() if the options "ena…

…blePacketDebug" and "log" are enable

src/main/java/org/mariadb/jdbc/internal/io/LruTraceCache.java

@@ -56,9 +56,7 @@
 
 import java.time.Instant;
 import java.time.format.DateTimeFormatter;
-import java.util.LinkedHashMap;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 
 public class LruTraceCache extends LinkedHashMap<Instant, TraceObject> {
 
@@ -76,7 +74,7 @@ protected boolean removeEldestEntry(Map.Entry<Instant, TraceObject> eldest) {
      *
      * @return trace cache value
      */
-    public String printStack() {
+    public synchronized String printStack() {
         StringBuilder sb = new StringBuilder();
         Set<Map.Entry<Instant, TraceObject>> set = entrySet();
         for (Map.Entry<Instant, TraceObject> entry : set) {
@@ -118,10 +116,10 @@ public String printStack() {
     /**
      * Permit to clear array's of array, to help garbage.
      */
-    public void clearMemory() {
-        Set<Map.Entry<Instant, TraceObject>> set = entrySet();
-        for (Map.Entry<Instant, TraceObject> entry : set) {
-            entry.getValue().remove();
+    public synchronized void clearMemory() {
+        Collection<TraceObject> traceObjects = values();
+        for (TraceObject traceObject : traceObjects) {
+            traceObject.remove();
         }
         this.clear();
     }