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diff --git a/src/io/appium/droiddriver/util/Preconditions.java b/src/io/appium/droiddriver/util/Preconditions.java
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+++ b/src/io/appium/droiddriver/util/Preconditions.java
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+/*
+ * Copyright (C) 2013 DroidDriver committers
+ *
+ * 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 io.appium.droiddriver.util;
+
+/**
+ * Simple static methods to be called at the start of your own methods to verify
+ * correct arguments and state.
+ */
+public final class Preconditions {
+  private Preconditions() {}
+
+  /**
+   * Ensures that an object reference passed as a parameter to the calling
+   * method is not null.
+   *
+   * @param reference an object reference
+   * @return the non-null reference that was validated
+   * @throws NullPointerException if {@code reference} is null
+   */
+  public static <T> T checkNotNull(T reference) {
+    if (reference == null) {
+      throw new NullPointerException();
+    }
+    return reference;
+  }
+}