Adjust AbstractListFilter.toString()

to produce a similar styled output like the other toString() methods and
add unit-test for the method.

smack-core/src/main/java/org/jivesoftware/smack/filter/AbstractListFilter.java

@@ -19,6 +19,7 @@ package org.jivesoftware.smack.filter;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Iterator;
 import java.util.List;
 
 import org.jivesoftware.smack.util.Objects;
@@ -68,9 +69,13 @@ public abstract class AbstractListFilter implements PacketFilter {
     public final String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append(getClass().getSimpleName());
-        sb.append(" (");
-        for (PacketFilter filter : filters) {
-            sb.append(' ' + filter.toString() + ',');
+        sb.append(": (");
+        for (Iterator<PacketFilter> it = filters.iterator(); it.hasNext();) {
+            PacketFilter filter = it.next();
+            sb.append(filter.toString());
+            if (it.hasNext()) {
+                sb.append(", ");
+            }
         }
         sb.append(")");
         return sb.toString();

smack-core/src/test/java/org/jivesoftware/smack/filters/FilterToStringTest.java

@@ -0,0 +1,42 @@
+/**
+ *
+ * Copyright 2015 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.filters;
+
+import static org.junit.Assert.assertEquals;
+
+import org.jivesoftware.smack.filter.AndFilter;
+import org.jivesoftware.smack.filter.MessageWithBodiesFilter;
+import org.jivesoftware.smack.filter.StanzaIdFilter;
+import org.jivesoftware.smack.filter.ThreadFilter;
+import org.junit.Test;
+
+/**
+ * 
+ */
+public class FilterToStringTest {
+
+    @Test
+    public void abstractListFilterToStringTest() {
+        AndFilter andFilter = new AndFilter();
+        andFilter.addFilter(new StanzaIdFilter("foo"));
+        andFilter.addFilter(new ThreadFilter("42"));
+        andFilter.addFilter(MessageWithBodiesFilter.INSTANCE);
+
+        final String res =andFilter.toString();
+        assertEquals("AndFilter: (StanzaIdFilter: id=foo, ThreadFilter: thread=42, MessageWithBodiesFilter)", res);
+    }
+}