Add Pair utility class

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

@@ -0,0 +1,64 @@
+/**
+ *
+ * Copyright 2020 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.util;
+
+public final class Pair<F, S> {
+
+    private final F first;
+    private final S second;
+
+    private Pair(F first, S second) {
+        this.first = first;
+        this.second = second;
+    }
+
+    public static <F extends Object, S extends Object> Pair<F, S> create(F first, S second) {
+        return new Pair<>(first, second);
+    }
+
+    public static <F extends Object, S extends Object> Pair<F, S> createAndInitHashCode(F first, S second) {
+        Pair<F, S> pair = new Pair<>(first, second);
+        pair.hashCode();
+        return pair;
+    }
+
+    public F getFirst() {
+        return first;
+    }
+
+    public S getSecond() {
+        return second;
+    }
+
+    private final HashCode.Cache hashCodeCache = new HashCode.Cache();
+
+    @Override
+    public int hashCode() {
+        return hashCodeCache.getHashCode(c ->
+            c.append(first)
+             .append(second)
+        );
+    }
+
+    @Override
+    public boolean equals(Object object) {
+        return EqualsUtil.equals(this, object, (e, o) ->
+            e.append(first, o.first)
+             .append(second, o.second)
+        );
+    }
+}