Remove trailing comma in ConnectionException message

Also add SmackExceptionTest

smack-core/src/main/java/org/jivesoftware/smack/SmackException.java

@@ -175,13 +175,14 @@ public class SmackException extends Exception {
         }
 
         public static ConnectionException from(List<HostAddress> failedAddresses) {
+            final String DELIMITER = ", ";
             StringBuilder sb = new StringBuilder("The following addresses failed: ");
             for (HostAddress hostAddress : failedAddresses) {
                 sb.append(hostAddress.getErrorMessage());
-                sb.append(", ");
+                sb.append(DELIMITER);
             }
-            // Remove the last whitespace
-            sb.deleteCharAt(sb.length() - 1);
+            // Remove the last delimiter
+            sb.setLength(sb.length() - DELIMITER.length());
             return new ConnectionException(sb.toString(), failedAddresses);
         }
 

smack-core/src/test/java/org/jivesoftware/smack/SmackExceptionTest.java

@@ -0,0 +1,48 @@
+/**
+ *
+ * Copyright © 2014 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jivesoftware.smack;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.LinkedList;
+import java.util.List;
+
+import org.jivesoftware.smack.SmackException.ConnectionException;
+import org.jivesoftware.smack.util.dns.HostAddress;
+import org.junit.Test;
+
+public class SmackExceptionTest {
+
+    @Test
+    public void testConnectionException() {
+        List<HostAddress> failedAddresses = new LinkedList<HostAddress>();
+
+        HostAddress hostAddress = new HostAddress("foo.bar.example", 1234);
+        hostAddress.setException(new Exception("Failed for some reason"));
+        failedAddresses.add(hostAddress);
+
+        hostAddress = new HostAddress("barz.example", 5678);
+        hostAddress.setException(new Exception("Failed for some other reason"));
+        failedAddresses.add(hostAddress);
+
+        ConnectionException connectionException = ConnectionException.from(failedAddresses);
+        String message = connectionException.getMessage();
+        assertEquals("The following addresses failed: foo.bar.example:1234 Exception: Failed for some reason, barz.example:5678 Exception: Failed for some other reason",
+                        message);
+    }
+
+}