Fix static validation issues

JAVA-3927

config/findbugs-exclude.xml

@@ -190,4 +190,10 @@
         <Bug pattern="VA_FORMAT_STRING_USES_NEWLINE"/>
     </Match>
 
+    <!-- The return value of Condition.awaitNanos is ignored on purpose for infinite timeouts. -->
+    <Match>
+        <Class name="com.mongodb.internal.connection.DefaultConnectionPool$OpenConcurrencyLimiter"/>
+        <Method name="awaitNanos"/>
+        <Bug pattern="RV_RETURN_VALUE_IGNORED_BAD_PRACTICE"/>
+    </Match>
 </FindBugsFilter>

driver-core/src/main/com/mongodb/internal/Timeout.java

@@ -1,10 +1,26 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * 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 com.mongodb.internal;
 
 import com.mongodb.annotations.Immutable;
 
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
 
+import static com.mongodb.assertions.Assertions.notNull;
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
 
 /**
@@ -28,7 +44,7 @@ private Timeout(final long durationNanos, final long startNanos) {
      * @see #startNow(long)
      */
     public static Timeout startNow(final long duration, final TimeUnit unit) {
-        return startNow(unit.toNanos(duration));
+        return startNow(notNull("unit", unit).toNanos(duration));
     }
 
     /**
@@ -65,8 +81,8 @@ public static Timeout immediate() {
      * Returns duration as per {@link #startNow(long)}.
      * The duration is converted to the specified {@code unit} via {@link TimeUnit#convert(long, TimeUnit)}.
      */
-    public long duration(TimeUnit unit) {
-        return unit.convert(durationNanos, NANOSECONDS);
+    public long duration(final TimeUnit unit) {
+        return notNull("unit", unit).convert(durationNanos, NANOSECONDS);
     }
 
     /**
@@ -151,9 +167,9 @@ public int hashCode() {
 
     @Override
     public String toString() {
-        return "Timeout{" +
-                "durationNanos=" + durationNanos +
-                ", startNanos=" + startNanos +
-                '}';
+        return "Timeout{"
+                + "durationNanos=" + durationNanos
+                + ", startNanos=" + startNanos
+                + '}';
     }
 }

driver-core/src/main/com/mongodb/internal/connection/DefaultConnectionPool.java

@@ -818,8 +818,11 @@ private PooledConnection acquirePermitOrGetAvailableOpenConnection(final boolean
                     addLastDesiredConnectionSlot();
                 }
                 long remainingNanos = timeout.remainingNanosOrInfinite();
-                while (permits == 0
-                        && (availableConnection = tryGetAvailable ? tryGetAndRemoveFirstDesiredConnectionSlot() : null) == null) {
+                while (permits == 0) {
+                    availableConnection = tryGetAvailable ? tryGetAndRemoveFirstDesiredConnectionSlot() : null;
+                    if (availableConnection != null) {
+                        break;
+                    }
                     if (Timeout.expired(remainingNanos)) {
                         throw createTimeoutException(timeout);
                     }
@@ -929,7 +932,7 @@ private PooledConnection openAndReleasePermit(
         }
 
         @Nullable
-        private <T> T returnValue(T value, @Nullable SingleResultCallback<? super T> callback) {
+        private <T> T returnValue(final T value, @Nullable final SingleResultCallback<? super T> callback) {
             if (callback == null) {
                 return value;
             } else {
@@ -939,7 +942,8 @@ private <T> T returnValue(T value, @Nullable SingleResultCallback<? super T> cal
         }
 
         @Nullable
-        private <T> T throwException(RuntimeException e, @Nullable SingleResultCallback<? super T> callback) throws RuntimeException {
+        private <T> T throwException(final RuntimeException e, @Nullable final SingleResultCallback<? super T> callback)
+                throws RuntimeException {
             if (callback == null) {
                 throw e;
             } else {

driver-core/src/test/unit/com/mongodb/internal/connection/ConcurrentPoolTest.java

@@ -172,7 +172,7 @@ public void whenEnsuringMinSizeShouldNotInitializePooledItemIfNotRequested() {
     public void whenEnsuringMinSizeShouldInitializePooledItemIfRequested() {
         pool = new ConcurrentPool<TestCloseable>(3, new TestItemFactory());
 
-        pool.ensureMinSize(1, TestCloseable.initializeAction);
+        pool.ensureMinSize(1, TestCloseable.INIT_ACTION);
         assertTrue(pool.get().isInitialized());
     }
 
@@ -181,7 +181,7 @@ public void testThatEnsuringMinSizeReleasesPermitIfCreateFails() {
         pool = new ConcurrentPool<TestCloseable>(1, new TestItemFactory(true));
 
         try {
-            pool.ensureMinSize(1, TestCloseable.initializeAction);
+            pool.ensureMinSize(1, TestCloseable.INIT_ACTION);
             fail();
         } catch (MongoException e) {
             // expected
@@ -253,7 +253,7 @@ public ConcurrentPool.Prune shouldPrune(final TestCloseable testCloseable) {
     }
 
     static class TestCloseable implements Closeable {
-        private static final Function<TestCloseable, Optional<TestCloseable>> initializeAction = connection -> {
+        private static final Function<TestCloseable, Optional<TestCloseable>> INIT_ACTION = connection -> {
             connection.initialized = true;
             return Optional.of(connection);
         };