Added ListHelper.java

core/src/main/java/com/danimahardhika/android/helpers/core/ListHelper.java

@@ -0,0 +1,44 @@
+package com.danimahardhika.android.helpers.core;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+/*
+ * Android Helpers
+ *
+ * Copyright (c) 2017 Dani Mahardhika
+ *
+ * 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.
+ */
+
+public class ListHelper {
+
+    public static <T> Collection<T> intersect(Collection <? extends T> a, Collection <? extends T> b) {
+        Collection <T> result = new ArrayList<>();
+
+        for (T t : a) {
+            if (b.remove(t)) result.add(t);
+        }
+        return result;
+    }
+
+    public static <T> Collection<T> difference(Collection <? extends T> a, Collection <? extends T> b) {
+        Collection <T> result = new ArrayList<>();
+        result.addAll(b);
+
+        for (T t : a) {
+            result.remove(t);
+        }
+        return result;
+    }
+}