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https://issues.apache.org/jira/browse/FLINK-3700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15236058#comment-15236058
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ASF GitHub Bot commented on FLINK-3700:
---------------------------------------
Github user ZackPierce commented on a diff in the pull request:
https://github.com/apache/flink/pull/1853#discussion_r59289246
--- Diff: flink-core/src/main/java/org/apache/flink/util/Preconditions.java
---
@@ -0,0 +1,213 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.
+ */
+
+//
----------------------------------------------------------------------------
+// This class is largely adapted from
"com.google.common.base.Preconditions",
+// which is part of the "Guava" library.
+//
+// Because of frequent issues with dependency conflicts, this class was
+// added to the Flink code base to reduce dependency on Guava.
+//
----------------------------------------------------------------------------
+
+package org.apache.flink.util;
+
+import org.apache.flink.annotation.Internal;
+
+import javax.annotation.Nullable;
+
+/**
+ * A collection of static utility methods to validate input.
+ *
+ * <p>This class is modelled after Google Guava's Preconditions class, and
partly takes code
+ * from that class. We add this code to the Flink code base in order to
reduce external
+ * dependencies.
+ */
+@Internal
+public final class Preconditions {
+
+ //
------------------------------------------------------------------------
+ // Null checks
+ //
------------------------------------------------------------------------
+
+ /**
+ * Ensures that the given object reference is not null.
+ * Upon violation, a {@code NullPointerException} with no message is
thrown.
+ *
+ * @param reference The object reference
+ * @return The object reference itself (generically typed).
+ *
+ * @throws NullPointerException Thrown, if the passed reference was
null.
+ */
+ public static <T> T checkNotNull(T reference) {
--- End diff --
For what it is worth, `Objects.requireNonNull` has overloads with the same
signature (as this and the next method down), and is [present in the JDK since
1.7](https://docs.oracle.com/javase/7/docs/api/java/util/Objects.html#requireNonNull(T)).
Using `requireNonNull` instead may help reduce the burden of semi-standard
code that Flink reimplements.
> Replace Guava Preconditions class with Flink Preconditions
> ----------------------------------------------------------
>
> Key: FLINK-3700
> URL: https://issues.apache.org/jira/browse/FLINK-3700
> Project: Flink
> Issue Type: Improvement
> Components: Core
> Affects Versions: 1.0.0
> Reporter: Stephan Ewen
> Assignee: Stephan Ewen
>
> In order to reduce the dependency on Guava (which has cause us quite a bit of
> pain in the past with its version conflicts), I suggest to add a Flink
> {{Preconditions}} class.
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