Introduce FormFieldChildElement and make FormField immutable

smack-core/src/main/java/org/jivesoftware/smack/util/CollectionUtil.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2015-2018 Florian Schmaus
+ * Copyright 2015-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -49,4 +49,10 @@ public class CollectionUtil {
     public interface Predicate<T> {
         boolean test(T t);
     }
+
+    public static <T> ArrayList<T> newListWith(Collection<? extends T> collection) {
+        ArrayList<T> arrayList = new ArrayList<>(collection.size());
+        arrayList.addAll(collection);
+        return arrayList;
+    }
 }

smack-core/src/main/java/org/jivesoftware/smack/util/MultiMap.java

@@ -22,6 +22,7 @@ import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Set;
 
 /**
@@ -57,7 +58,11 @@ public class MultiMap<K, V> {
      * @param size the initial capacity.
      */
     public MultiMap(int size) {
-        map = new LinkedHashMap<>(size);
+        this(new LinkedHashMap<>(size));
+    }
+
+    private MultiMap(Map<K, List<V>> map) {
+        this.map = map;
     }
 
     public int size() {
@@ -235,6 +240,18 @@ public class MultiMap<K, V> {
         return entrySet;
     }
 
+    public MultiMap<K, V> asUnmodifiableMultiMap() {
+        LinkedHashMap<K, List<V>> mapCopy = new LinkedHashMap<>(map.size());
+        for (Entry<K, List<V>> entry : map.entrySet()) {
+            K key = entry.getKey();
+            List<V> values = entry.getValue();
+
+            mapCopy.put(key, Collections.unmodifiableList(values));
+        }
+
+        return new MultiMap<K, V>(Collections.unmodifiableMap(mapCopy));
+    }
+
     private static final class SimpleMapEntry<K, V> implements Map.Entry<K, V> {
 
         private final K key;

smack-core/src/main/java/org/jivesoftware/smack/util/XmlStringBuilder.java

@@ -273,6 +273,15 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
         return this;
     }
 
+    public <E extends Enum<?>> XmlStringBuilder attribute(String name, E value, E implicitDefault) {
+        if (value == null || value == implicitDefault) {
+            return this;
+        }
+
+        attribute(name, value.toString());
+        return this;
+    }
+
     public XmlStringBuilder attribute(String name, int value) {
         assert name != null;
         return attribute(name, String.valueOf(value));

smack-core/src/test/java/org/jivesoftware/smack/test/util/SmackTestSuite.java

@@ -18,6 +18,7 @@ package org.jivesoftware.smack.test.util;
 
 import java.util.Base64;
 
+import org.jivesoftware.smack.SmackConfiguration;
 import org.jivesoftware.smack.util.stringencoder.Base64.Encoder;
 
 /**
@@ -27,6 +28,7 @@ import org.jivesoftware.smack.util.stringencoder.Base64.Encoder;
 public class SmackTestSuite {
 
     static {
+        SmackConfiguration.getVersion();
         org.jivesoftware.smack.util.stringencoder.Base64.setEncoder(new Encoder() {
 
             @Override