--- old/src/java.naming/share/classes/com/sun/jndi/ldap/pool/Connections.java	2016-12-14 16:02:19.512146102 +0000
+++ new/src/java.naming/share/classes/com/sun/jndi/ldap/pool/Connections.java	2016-12-14 16:02:19.384146096 +0000
@@ -27,7 +27,6 @@
 
 import java.util.ArrayList; // JDK 1.2
 import java.util.List;
-import java.util.Iterator;
 
 import java.lang.ref.Reference;
 import java.lang.ref.SoftReference;
@@ -291,22 +290,27 @@
      * @return true if no more connections in list
      */
     synchronized boolean expire(long threshold) {
-        Iterator<ConnectionDesc> iter = conns.iterator();
-        ConnectionDesc entry;
-        while (iter.hasNext()) {
-            entry = iter.next();
-            if (entry.expire(threshold)) {
-                d("expire(): removing ", entry);
-                td("Expired ", entry);
-
-                iter.remove();  // remove from pool
+        List<ConnectionDesc> clonedConns;
+        synchronized(this) {
+            clonedConns = new ArrayList<>(conns);
+        }
+        List<ConnectionDesc> expired = new ArrayList<>();
 
-                // Don't need to call notify() because we're
-                // removing only idle connections. If there were
-                // idle connections, then there should be no waiters.
+        for (ConnectionDesc entry : clonedConns) {
+            d("expire(): ", entry);
+            if (entry.expire(threshold)) {
+                expired.add(entry);
+                td("expire(): Expired ", entry);
             }
         }
-        return conns.isEmpty();  // whether whole list has 'expired'
+
+        synchronized (this) {
+            conns.removeAll(expired);
+            // Don't need to call notify() because we're
+            // removing only idle connections. If there were
+            // idle connections, then there should be no waiters.
+            return conns.isEmpty();  // whether whole list has 'expired'
+        }
     }
 
     /**