diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/exceptions/ClientExceptionsUtil.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/exceptions/ClientExceptionsUtil.java
index 71999ad269f..fd9936dc502 100644
--- a/hbase-client/src/main/java/org/apache/hadoop/hbase/exceptions/ClientExceptionsUtil.java
+++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/exceptions/ClientExceptionsUtil.java
@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.hbase.exceptions;
 
+import com.google.errorprone.annotations.RestrictedApi;
 import java.io.EOFException;
 import java.io.IOException;
 import java.io.SyncFailedException;
@@ -120,6 +121,10 @@ public final class ClientExceptionsUtil {
    * For test only. Usually you should use the {@link #isConnectionException(Throwable)} method
    * below.
    */
+  @RestrictedApi(explanation = "Should only be called in tests", link = "",
+      allowedOnPath = ".*/src/test/.*")
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "test only")
   public static Set<Class<? extends Throwable>> getConnectionExceptionTypes() {
     return CONNECTION_EXCEPTION_TYPES;
   }
diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/RequestConverter.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/RequestConverter.java
index 13e85f91c95..f678a43986d 100644
--- a/hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/RequestConverter.java
+++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/RequestConverter.java
@@ -839,32 +839,20 @@ public final class RequestConverter {
     return builder.build();
   }
 
-  /**
-   * @see #buildRollWALWriterRequest()
-   */
-  private static RollWALWriterRequest ROLL_WAL_WRITER_REQUEST =
-    RollWALWriterRequest.newBuilder().build();
-
   /**
    * Create a new RollWALWriterRequest
    * @return a ReplicateWALEntryRequest
    */
   public static RollWALWriterRequest buildRollWALWriterRequest() {
-    return ROLL_WAL_WRITER_REQUEST;
+    return RollWALWriterRequest.getDefaultInstance();
   }
 
-  /**
-   * @see #buildGetServerInfoRequest()
-   */
-  private static GetServerInfoRequest GET_SERVER_INFO_REQUEST =
-    GetServerInfoRequest.newBuilder().build();
-
   /**
    * Create a new GetServerInfoRequest
    * @return a GetServerInfoRequest
    */
   public static GetServerInfoRequest buildGetServerInfoRequest() {
-    return GET_SERVER_INFO_REQUEST;
+    return GetServerInfoRequest.getDefaultInstance();
   }
 
   /**
@@ -1241,18 +1229,12 @@ public final class RequestConverter {
       .addAllOptions(ClusterMetricsBuilder.toOptions(options)).build();
   }
 
-  /**
-   * @see #buildCatalogScanRequest
-   */
-  private static final RunCatalogScanRequest CATALOG_SCAN_REQUEST =
-    RunCatalogScanRequest.newBuilder().build();
-
   /**
    * Creates a request for running a catalog scan
    * @return A {@link RunCatalogScanRequest}
    */
   public static RunCatalogScanRequest buildCatalogScanRequest() {
-    return CATALOG_SCAN_REQUEST;
+    return RunCatalogScanRequest.getDefaultInstance();
   }
 
   /**
@@ -1263,32 +1245,20 @@ public final class RequestConverter {
     return EnableCatalogJanitorRequest.newBuilder().setEnable(enable).build();
   }
 
-  /**
-   * @see #buildIsCatalogJanitorEnabledRequest()
-   */
-  private static final IsCatalogJanitorEnabledRequest IS_CATALOG_JANITOR_ENABLED_REQUEST =
-    IsCatalogJanitorEnabledRequest.newBuilder().build();
-
   /**
    * Creates a request for querying the master whether the catalog janitor is enabled
    * @return A {@link IsCatalogJanitorEnabledRequest}
    */
   public static IsCatalogJanitorEnabledRequest buildIsCatalogJanitorEnabledRequest() {
-    return IS_CATALOG_JANITOR_ENABLED_REQUEST;
+    return IsCatalogJanitorEnabledRequest.getDefaultInstance();
   }
 
-  /**
-   * @see #buildRunCleanerChoreRequest()
-   */
-  private static final RunCleanerChoreRequest CLEANER_CHORE_REQUEST =
-    RunCleanerChoreRequest.newBuilder().build();
-
   /**
    * Creates a request for running cleaner chore
    * @return A {@link RunCleanerChoreRequest}
    */
   public static RunCleanerChoreRequest buildRunCleanerChoreRequest() {
-    return CLEANER_CHORE_REQUEST;
+    return RunCleanerChoreRequest.getDefaultInstance();
   }
 
   /**
@@ -1299,18 +1269,12 @@ public final class RequestConverter {
     return SetCleanerChoreRunningRequest.newBuilder().setOn(on).build();
   }
 
-  /**
-   * @see #buildIsCleanerChoreEnabledRequest()
-   */
-  private static final IsCleanerChoreEnabledRequest IS_CLEANER_CHORE_ENABLED_REQUEST =
-    IsCleanerChoreEnabledRequest.newBuilder().build();
-
   /**
    * Creates a request for querying the master whether the cleaner chore is enabled
    * @return A {@link IsCleanerChoreEnabledRequest}
    */
   public static IsCleanerChoreEnabledRequest buildIsCleanerChoreEnabledRequest() {
-    return IS_CLEANER_CHORE_ENABLED_REQUEST;
+    return IsCleanerChoreEnabledRequest.getDefaultInstance();
   }
 
   /**
@@ -1530,34 +1494,25 @@ public final class RequestConverter {
     return builder.build();
   }
 
-  private static final GetSpaceQuotaRegionSizesRequest GET_SPACE_QUOTA_REGION_SIZES_REQUEST =
-    GetSpaceQuotaRegionSizesRequest.newBuilder().build();
-
   /**
    * Returns a {@link GetSpaceQuotaRegionSizesRequest} object.
    */
   public static GetSpaceQuotaRegionSizesRequest buildGetSpaceQuotaRegionSizesRequest() {
-    return GET_SPACE_QUOTA_REGION_SIZES_REQUEST;
+    return GetSpaceQuotaRegionSizesRequest.getDefaultInstance();
   }
 
-  private static final GetSpaceQuotaSnapshotsRequest GET_SPACE_QUOTA_SNAPSHOTS_REQUEST =
-    GetSpaceQuotaSnapshotsRequest.newBuilder().build();
-
   /**
    * Returns a {@link GetSpaceQuotaSnapshotsRequest} object.
    */
   public static GetSpaceQuotaSnapshotsRequest buildGetSpaceQuotaSnapshotsRequest() {
-    return GET_SPACE_QUOTA_SNAPSHOTS_REQUEST;
+    return GetSpaceQuotaSnapshotsRequest.getDefaultInstance();
   }
 
-  private static final GetQuotaStatesRequest GET_QUOTA_STATES_REQUEST =
-    GetQuotaStatesRequest.newBuilder().build();
-
   /**
    * Returns a {@link GetQuotaStatesRequest} object.
    */
   public static GetQuotaStatesRequest buildGetQuotaStatesRequest() {
-    return GET_QUOTA_STATES_REQUEST;
+    return GetQuotaStatesRequest.getDefaultInstance();
   }
 
   public static DecommissionRegionServersRequest
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/CryptoCipherProvider.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/CryptoCipherProvider.java
index 8eb4bdea71b..7f5c58883f2 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/CryptoCipherProvider.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/CryptoCipherProvider.java
@@ -30,6 +30,8 @@ public final class CryptoCipherProvider implements CipherProvider {
 
   private static CryptoCipherProvider instance;
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static CryptoCipherProvider getInstance() {
     if (instance != null) {
       return instance;
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/DefaultCipherProvider.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/DefaultCipherProvider.java
index 33e19575d94..a4c3f3b7ca8 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/DefaultCipherProvider.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/io/crypto/DefaultCipherProvider.java
@@ -30,6 +30,8 @@ public final class DefaultCipherProvider implements CipherProvider {
 
   private static DefaultCipherProvider instance;
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static DefaultCipherProvider getInstance() {
     if (instance != null) {
       return instance;
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/io/util/BlockIOUtils.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/io/util/BlockIOUtils.java
index 86c6317556b..9641c72dfbc 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/io/util/BlockIOUtils.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/io/util/BlockIOUtils.java
@@ -367,10 +367,6 @@ public final class BlockIOUtils {
         } catch (InvocationTargetException e) {
           throw new IOException("Encountered an exception when invoking ByteBuffer positioned read"
             + " when trying to read " + bytesRead + " bytes from position " + position, e);
-        } catch (NullPointerException e) {
-          throw new IOException("something is null");
-        } catch (Exception e) {
-          throw e;
         }
         if (ret < 0) {
           throw new IOException("Premature EOF from inputStream (positional read returned " + ret
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/security/Superusers.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/security/Superusers.java
index 417c59c7d02..d4f3f16478f 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/security/Superusers.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/security/Superusers.java
@@ -19,14 +19,14 @@ package org.apache.hadoop.hbase.security;
 
 import java.io.IOException;
 import java.util.Collection;
-import java.util.HashSet;
-import java.util.Set;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.AuthUtil;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableSet;
+
 /**
  * Keeps lists of superusers and super groups loaded from HBase configuration, checks if certain
  * user is regarded as superuser.
@@ -38,8 +38,8 @@ public final class Superusers {
   /** Configuration key for superusers */
   public static final String SUPERUSER_CONF_KEY = "hbase.superuser"; // Not getting a name
 
-  private static Set<String> superUsers;
-  private static Set<String> superGroups;
+  private static ImmutableSet<String> superUsers;
+  private static ImmutableSet<String> superGroups;
   private static User systemUser;
 
   private Superusers() {
@@ -53,8 +53,8 @@ public final class Superusers {
    * @throws IllegalStateException if current user is null
    */
   public static void initialize(Configuration conf) throws IOException {
-    superUsers = new HashSet<>();
-    superGroups = new HashSet<>();
+    ImmutableSet.Builder<String> superUsersBuilder = ImmutableSet.builder();
+    ImmutableSet.Builder<String> superGroupsBuilder = ImmutableSet.builder();
     systemUser = User.getCurrent();
 
     if (systemUser == null) {
@@ -64,17 +64,19 @@ public final class Superusers {
 
     String currentUser = systemUser.getShortName();
     LOG.trace("Current user name is {}", currentUser);
-    superUsers.add(currentUser);
+    superUsersBuilder.add(currentUser);
 
     String[] superUserList = conf.getStrings(SUPERUSER_CONF_KEY, new String[0]);
     for (String name : superUserList) {
       if (AuthUtil.isGroupPrincipal(name)) {
         // Let's keep the '@' for distinguishing from user.
-        superGroups.add(name);
+        superGroupsBuilder.add(name);
       } else {
-        superUsers.add(name);
+        superUsersBuilder.add(name);
       }
     }
+    superUsers = superUsersBuilder.build();
+    superGroups = superGroupsBuilder.build();
   }
 
   /**
@@ -113,14 +115,20 @@ public final class Superusers {
     return superUsers.contains(user) || superGroups.contains(user);
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "immutable")
   public static Collection<String> getSuperUsers() {
     return superUsers;
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "immutable")
   public static Collection<String> getSuperGroups() {
     return superGroups;
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "by design")
   public static User getSystemUser() {
     return systemUser;
   }
diff --git a/hbase-metrics/pom.xml b/hbase-metrics/pom.xml
index ee7a61ed931..ad8d2367649 100644
--- a/hbase-metrics/pom.xml
+++ b/hbase-metrics/pom.xml
@@ -76,6 +76,12 @@
       <groupId>io.dropwizard.metrics</groupId>
       <artifactId>metrics-core</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.github.stephenc.findbugs</groupId>
+      <artifactId>findbugs-annotations</artifactId>
+      <scope>compile</scope>
+      <optional>true</optional>
+    </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
diff --git a/hbase-metrics/src/main/java/org/apache/hadoop/hbase/metrics/impl/FastLongHistogram.java b/hbase-metrics/src/main/java/org/apache/hadoop/hbase/metrics/impl/FastLongHistogram.java
index b1b47e3904e..768435d1eb1 100644
--- a/hbase-metrics/src/main/java/org/apache/hadoop/hbase/metrics/impl/FastLongHistogram.java
+++ b/hbase-metrics/src/main/java/org/apache/hadoop/hbase/metrics/impl/FastLongHistogram.java
@@ -138,6 +138,8 @@ public class FastLongHistogram {
     /**
      * Computes the quantiles give the ratios.
      */
+    @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "FL_FLOATS_AS_LOOP_COUNTERS",
+        justification = "valid usage")
     public long[] getQuantiles(double[] quantiles) {
       if (!hasData) {
         // No data yet.
@@ -266,10 +268,6 @@ public class FastLongHistogram {
     this.bins = new Bins(bins, numOfBins, 0.01, 0.999);
   }
 
-  private FastLongHistogram(Bins bins) {
-    this.bins = bins;
-  }
-
   /**
    * Adds a value to the histogram.
    */
diff --git a/hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/RESTServlet.java b/hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/RESTServlet.java
index 66834f36176..79760aead9d 100644
--- a/hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/RESTServlet.java
+++ b/hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/RESTServlet.java
@@ -53,6 +53,8 @@ public class RESTServlet implements Constants {
   }
 
   /** Returns the RESTServlet singleton instance */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public synchronized static RESTServlet getInstance() {
     assert (INSTANCE != null);
     return INSTANCE;
@@ -66,8 +68,10 @@ public class RESTServlet implements Constants {
   /**
    * @param conf         Existing configuration to use in rest servlet
    * @param userProvider the login user provider
-   * @return the RESTServlet singleton instance n
+   * @return the RESTServlet singleton instance
    */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public synchronized static RESTServlet getInstance(Configuration conf, UserProvider userProvider)
     throws IOException {
     if (INSTANCE == null) {
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/FileLink.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/FileLink.java
index 8fbaa775391..86f8f935334 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/FileLink.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/FileLink.java
@@ -117,12 +117,10 @@ public class FileLink {
         res = in.read();
       } catch (FileNotFoundException e) {
         res = tryOpen().read();
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        res = tryOpen().read();
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        res = tryOpen().read();
       }
-      if (res > 0) pos += 1;
+      if (res > 0) {
+        pos += 1;
+      }
       return res;
     }
 
@@ -138,12 +136,10 @@ public class FileLink {
         n = in.read(b, off, len);
       } catch (FileNotFoundException e) {
         n = tryOpen().read(b, off, len);
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        n = tryOpen().read(b, off, len);
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        n = tryOpen().read(b, off, len);
       }
-      if (n > 0) pos += n;
+      if (n > 0) {
+        pos += n;
+      }
       assert (in.getPos() == pos);
       return n;
     }
@@ -155,10 +151,6 @@ public class FileLink {
         n = in.read(position, buffer, offset, length);
       } catch (FileNotFoundException e) {
         n = tryOpen().read(position, buffer, offset, length);
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        n = tryOpen().read(position, buffer, offset, length);
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        n = tryOpen().read(position, buffer, offset, length);
       }
       return n;
     }
@@ -174,10 +166,6 @@ public class FileLink {
         in.readFully(position, buffer, offset, length);
       } catch (FileNotFoundException e) {
         tryOpen().readFully(position, buffer, offset, length);
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        tryOpen().readFully(position, buffer, offset, length);
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        tryOpen().readFully(position, buffer, offset, length);
       }
     }
 
@@ -189,13 +177,11 @@ public class FileLink {
         skipped = in.skip(n);
       } catch (FileNotFoundException e) {
         skipped = tryOpen().skip(n);
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        skipped = tryOpen().skip(n);
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        skipped = tryOpen().skip(n);
       }
 
-      if (skipped > 0) pos += skipped;
+      if (skipped > 0) {
+        pos += skipped;
+      }
       return skipped;
     }
 
@@ -205,10 +191,6 @@ public class FileLink {
         return in.available();
       } catch (FileNotFoundException e) {
         return tryOpen().available();
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        return tryOpen().available();
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        return tryOpen().available();
       }
     }
 
@@ -218,10 +200,6 @@ public class FileLink {
         in.seek(pos);
       } catch (FileNotFoundException e) {
         tryOpen().seek(pos);
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        tryOpen().seek(pos);
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        tryOpen().seek(pos);
       }
       this.pos = pos;
     }
@@ -238,10 +216,6 @@ public class FileLink {
         res = in.seekToNewSource(targetPos);
       } catch (FileNotFoundException e) {
         res = tryOpen().seekToNewSource(targetPos);
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        res = tryOpen().seekToNewSource(targetPos);
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        res = tryOpen().seekToNewSource(targetPos);
       }
       if (res) pos = targetPos;
       return res;
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/FixedFileTrailer.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/FixedFileTrailer.java
index b358ad60689..134485135ed 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/FixedFileTrailer.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/FixedFileTrailer.java
@@ -388,7 +388,7 @@ public class FixedFileTrailer {
       bufferSize = (int) fileSize;
     }
 
-    HFileUtil.seekOnMultipleSources(istream, seekPoint);
+    istream.seek(seekPoint);
 
     ByteBuffer buf = ByteBuffer.allocate(bufferSize);
     istream.readFully(buf.array(), buf.arrayOffset(), buf.arrayOffset() + buf.limit());
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java
index 8e04580874f..097aaff27c8 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java
@@ -1471,7 +1471,7 @@ public class HFileBlock implements Cacheable {
       boolean peekIntoNextBlock, long fileOffset, boolean pread) throws IOException {
       if (!pread) {
         // Seek + read. Better for scanning.
-        HFileUtil.seekOnMultipleSources(istream, fileOffset);
+        istream.seek(fileOffset);
         long realOffset = istream.getPos();
         if (realOffset != fileOffset) {
           throw new IOException("Tried to seek to " + fileOffset + " to read " + size
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePreadReader.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePreadReader.java
index 25627c34f51..98401c46bee 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePreadReader.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePreadReader.java
@@ -73,10 +73,6 @@ public class HFilePreadReader extends HFileReaderImpl {
             if (LOG.isTraceEnabled()) {
               LOG.trace("Prefetch " + getPathOffsetEndStr(path, offset, end), e);
             }
-          } catch (NullPointerException e) {
-            LOG.warn(
-              "Stream moved/closed or prefetch cancelled?" + getPathOffsetEndStr(path, offset, end),
-              e);
           } catch (Exception e) {
             // Other exceptions are interesting
             LOG.warn("Prefetch " + getPathOffsetEndStr(path, offset, end), e);
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileUtil.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileUtil.java
deleted file mode 100644
index 612f127e11e..00000000000
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileUtil.java
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * 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.
- */
-package org.apache.hadoop.hbase.io.hfile;
-
-import java.io.IOException;
-import org.apache.hadoop.fs.FSDataInputStream;
-import org.apache.yetus.audience.InterfaceAudience;
-
-@InterfaceAudience.Private
-class HFileUtil {
-
-  /**
-   * guards against NullPointer utility which tries to seek on the DFSIS and will try an alternative
-   * source if the FSDataInputStream throws an NPE HBASE-17501 nnn
-   */
-  static public void seekOnMultipleSources(FSDataInputStream istream, long offset)
-    throws IOException {
-    try {
-      // attempt to seek inside of current blockReader
-      istream.seek(offset);
-    } catch (NullPointerException e) {
-      // retry the seek on an alternate copy of the data
-      // this can occur if the blockReader on the DFSInputStream is null
-      istream.seekToNewSource(offset);
-    }
-  }
-}
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/PrefetchExecutor.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/PrefetchExecutor.java
index 8f10a0f9782..9aafe7a7b6e 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/PrefetchExecutor.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/PrefetchExecutor.java
@@ -145,6 +145,8 @@ public final class PrefetchExecutor {
     return true;
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "OBL_UNSATISFIED_OBLIGATION",
+      justification = "false positive, try-with-resources ensures close is called.")
   public static void persistToFile(String path) throws IOException {
     prefetchedFileListPath = path;
     if (prefetchedFileListPath == null) {
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/namequeues/NamedQueueRecorder.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/namequeues/NamedQueueRecorder.java
index 38f63fd09be..efe512b1a85 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/namequeues/NamedQueueRecorder.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/namequeues/NamedQueueRecorder.java
@@ -43,7 +43,7 @@ public class NamedQueueRecorder {
   private final Disruptor<RingBufferEnvelope> disruptor;
   private final LogEventHandler logEventHandler;
 
-  private static NamedQueueRecorder namedQueueRecorder;
+  private static volatile NamedQueueRecorder namedQueueRecorder;
   private static boolean isInit = false;
   private static final Object LOCK = new Object();
 
@@ -71,6 +71,8 @@ public class NamedQueueRecorder {
     this.disruptor.start();
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static NamedQueueRecorder getInstance(Configuration conf) {
     if (namedQueueRecorder != null) {
       return namedQueueRecorder;
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/NoOpRegionSizeStore.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/NoOpRegionSizeStore.java
index dcc32d766b9..cb463b8729d 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/NoOpRegionSizeStore.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/NoOpRegionSizeStore.java
@@ -32,6 +32,8 @@ public final class NoOpRegionSizeStore implements RegionSizeStore {
   private NoOpRegionSizeStore() {
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static NoOpRegionSizeStore getInstance() {
     return INSTANCE;
   }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/policies/MissingSnapshotViolationPolicyEnforcement.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/policies/MissingSnapshotViolationPolicyEnforcement.java
index c747d0c8b3d..732318ac870 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/policies/MissingSnapshotViolationPolicyEnforcement.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/policies/MissingSnapshotViolationPolicyEnforcement.java
@@ -39,6 +39,8 @@ public final class MissingSnapshotViolationPolicyEnforcement
   private MissingSnapshotViolationPolicyEnforcement() {
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static SpaceViolationPolicyEnforcement getInstance() {
     return SINGLETON;
   }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ChunkCreator.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ChunkCreator.java
index a0dbf4e59e9..ba9cd9d13ec 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ChunkCreator.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ChunkCreator.java
@@ -114,7 +114,8 @@ public class ChunkCreator {
    * @param heapMemoryManager      the heapmemory manager
    * @return singleton MSLABChunkCreator
    */
-  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "LI_LAZY_INIT_STATIC",
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(
+      value = { "LI_LAZY_INIT_STATIC", "MS_EXPOSE_REP" },
       justification = "Method is called by single thread at the starting of RS")
   public static ChunkCreator initialize(int chunkSize, boolean offheap, long globalMemStoreSize,
     float poolSizePercentage, float initialCountPercentage, HeapMemoryManager heapMemoryManager,
@@ -127,6 +128,8 @@ public class ChunkCreator {
     return instance;
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static ChunkCreator getInstance() {
     return instance;
   }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HMobStore.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HMobStore.java
index 13b7cc022bb..b5396110db2 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HMobStore.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HMobStore.java
@@ -400,7 +400,7 @@ public class HMobStore extends HStore {
   private MobCell readCell(List<Path> locations, String fileName, Cell search,
     boolean cacheMobBlocks, long readPt, boolean readEmptyValueOnMobCellMiss) throws IOException {
     FileSystem fs = getFileSystem();
-    Throwable throwable = null;
+    IOException ioe = null;
     for (Path location : locations) {
       MobFile file = null;
       Path path = new Path(location, fileName);
@@ -411,7 +411,7 @@ public class HMobStore extends HStore {
           : file.readCell(search, cacheMobBlocks);
       } catch (IOException e) {
         mobFileCache.evictFile(fileName);
-        throwable = e;
+        ioe = e;
         if (
           (e instanceof FileNotFoundException) || (e.getCause() instanceof FileNotFoundException)
         ) {
@@ -422,14 +422,6 @@ public class HMobStore extends HStore {
         } else {
           throw e;
         }
-      } catch (NullPointerException e) { // HDFS 1.x - DFSInputStream.getBlockAt()
-        mobFileCache.evictFile(fileName);
-        LOG.debug("Fail to read the cell", e);
-        throwable = e;
-      } catch (AssertionError e) { // assert in HDFS 1.x - DFSInputStream.getBlockAt()
-        mobFileCache.evictFile(fileName);
-        LOG.debug("Fail to read the cell", e);
-        throwable = e;
       } finally {
         if (file != null) {
           mobFileCache.closeFile(file);
@@ -441,18 +433,15 @@ public class HMobStore extends HStore {
     if (readEmptyValueOnMobCellMiss) {
       return null;
     } else if (
-      (throwable instanceof FileNotFoundException)
-        || (throwable.getCause() instanceof FileNotFoundException)
+      (ioe instanceof FileNotFoundException) || (ioe.getCause() instanceof FileNotFoundException)
     ) {
       // The region is re-opened when FileNotFoundException is thrown.
       // This is not necessary when MOB files cannot be found, because the store files
       // in a region only contain the references to MOB files and a re-open on a region
       // doesn't help fix the lost MOB files.
-      throw new DoNotRetryIOException(throwable);
-    } else if (throwable instanceof IOException) {
-      throw (IOException) throwable;
+      throw new DoNotRetryIOException(ioe);
     } else {
-      throw new IOException(throwable);
+      throw ioe;
     }
   }
 
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NoLimitScannerContext.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NoLimitScannerContext.java
index 5b92cc07b57..94c97374305 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NoLimitScannerContext.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NoLimitScannerContext.java
@@ -45,9 +45,11 @@ public class NoLimitScannerContext extends ScannerContext {
   private static final ScannerContext NO_LIMIT = new NoLimitScannerContext();
 
   /**
-   * @return The static, immutable instance of {@link NoLimitScannerContext} to be used whenever
-   *         limits should not be enforced
+   * Returns the static, immutable instance of {@link NoLimitScannerContext} to be used whenever
+   * limits should not be enforced
    */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static final ScannerContext getInstance() {
     return NO_LIMIT;
   }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/StripeCompactionPolicy.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/StripeCompactionPolicy.java
index adcd41f3e26..f5be2b38038 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/StripeCompactionPolicy.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/StripeCompactionPolicy.java
@@ -421,6 +421,8 @@ public class StripeCompactionPolicy extends CompactionPolicy {
     return totalSize;
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "FL_FLOATS_AS_LOOP_COUNTERS",
+      justification = "valid usage")
   private Pair<Long, Integer> estimateTargetKvs(Collection<HStoreFile> files, double splitCount) {
     // If the size is larger than what we target, we don't want to split into proportionally
     // larger parts and then have to split again very soon. So, we will increase the multiplier
@@ -433,7 +435,10 @@ public class StripeCompactionPolicy extends CompactionPolicy {
     while (ratio > 1.0) {
       // Ratio of real to desired size if we increase the multiplier.
       double newRatio = totalSize / ((splitCount + 1.0) * targetPartSize);
-      if ((1.0 / newRatio) >= ratio) break; // New ratio is < 1.0, but further than the last one.
+      if ((1.0 / newRatio) >= ratio) {
+        // New ratio is < 1.0, but further than the last one.
+        break;
+      }
       ratio = newRatio;
       splitCount += 1.0;
     }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogWriter.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogWriter.java
index a94449fe01e..212788c940e 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogWriter.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogWriter.java
@@ -66,15 +66,10 @@ public class ProtobufLogWriter extends AbstractProtobufLogWriter implements FSHL
   @Override
   public void close() throws IOException {
     if (this.output != null) {
-      try {
-        if (!trailerWritten) {
-          writeWALTrailer();
-        }
-        this.output.close();
-      } catch (NullPointerException npe) {
-        // Can get a NPE coming up from down in DFSClient$DFSOutputStream#close
-        LOG.warn(npe.toString(), npe);
+      if (!trailerWritten) {
+        writeWALTrailer();
       }
+      this.output.close();
       this.output = null;
     }
   }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryStream.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryStream.java
index 1d9f868e52f..42509eaebff 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryStream.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryStream.java
@@ -321,6 +321,8 @@ class WALEntryStream implements Closeable {
     }
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "DCN_NULLPOINTER_EXCEPTION",
+      justification = "HDFS-4380")
   private void openReader(Path path) throws IOException {
     try {
       // Detect if this is a new file, if so get a new reader else
@@ -371,6 +373,8 @@ class WALEntryStream implements Closeable {
     }
   }
 
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "DCN_NULLPOINTER_EXCEPTION",
+      justification = "HDFS-4380")
   private void resetReader() throws IOException {
     try {
       currentEntry = null;
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/FsDelegationToken.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/FsDelegationToken.java
index 1eb88a3d12f..51961a92370 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/FsDelegationToken.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/FsDelegationToken.java
@@ -98,12 +98,7 @@ public class FsDelegationToken {
       userToken = userProvider.getCurrent().getToken(tokenKind, fs.getCanonicalServiceName());
       if (userToken == null) {
         hasForwardedToken = false;
-        try {
-          userToken = fs.getDelegationToken(renewer);
-        } catch (NullPointerException npe) {
-          // we need to handle NullPointerException in case HADOOP-10009 is missing
-          LOG.error("Failed to get token for " + renewer);
-        }
+        userToken = fs.getDelegationToken(renewer);
       } else {
         hasForwardedToken = true;
         LOG.info("Use the existing token: " + userToken);
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityLabelsCache.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityLabelsCache.java
index 22168c5513f..4b1d2f4d84f 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityLabelsCache.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityLabelsCache.java
@@ -75,9 +75,11 @@ public class VisibilityLabelsCache implements VisibilityLabelOrdinalProvider {
   }
 
   /**
-   * Creates the singleton instance, if not yet present, and returns the same. nn * @return
-   * Singleton instance of VisibilityLabelsCache n
+   * Creates the singleton instance, if not yet present, and returns the same.
+   * @return Singleton instance of VisibilityLabelsCache
    */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public synchronized static VisibilityLabelsCache createAndGet(ZKWatcher watcher,
     Configuration conf) throws IOException {
     // VisibilityLabelService#init() for different regions (in same RS) passes same instance of
@@ -96,6 +98,8 @@ public class VisibilityLabelsCache implements VisibilityLabelOrdinalProvider {
    * @return Singleton instance of VisibilityLabelsCache n * when this is called before calling
    *         {@link #createAndGet(ZKWatcher, Configuration)}
    */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
+      justification = "singleton pattern")
   public static VisibilityLabelsCache get() {
     // By the time this method is called, the singleton instance of VisibilityLabelsCache should
     // have been created.
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/util/BloomFilterUtil.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/util/BloomFilterUtil.java
index b35e8258ddf..7b8a5cd241a 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/util/BloomFilterUtil.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/util/BloomFilterUtil.java
@@ -76,6 +76,8 @@ public final class BloomFilterUtil {
    * This gets used in {@link #contains(ByteBuff, int, int, Hash, int, HashKey)}
    * @param random The random number source to use, or null to compute actual hashes
    */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "EI_EXPOSE_STATIC_REP2",
+      justification = "ignore for now, improve TestCompoundBloomFilter later")
   public static void setRandomGeneratorForTest(Random random) {
     randomGeneratorForTest = random;
   }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java
index 41505b92c6a..75572b4c53e 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/util/HBaseFsck.java
@@ -983,12 +983,9 @@ public class HBaseFsck extends Configured implements Closeable {
           start = CellUtil.cloneRow(startKv.get());
           Optional<Cell> endKv = hf.getLastKey();
           end = CellUtil.cloneRow(endKv.get());
-        } catch (IOException ioe) {
+        } catch (Exception ioe) {
           LOG.warn("Problem reading orphan file " + hfile + ", skipping");
           continue;
-        } catch (NullPointerException ioe) {
-          LOG.warn("Orphan file " + hfile + " is possibly corrupted HFile, skipping");
-          continue;
         } finally {
           if (hf != null) {
             hf.close();
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java
index be9fb23fa3c..32700950460 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java
@@ -504,8 +504,9 @@ public abstract class AbstractFSWALProvider<T extends AbstractFSWAL<?>> implemen
    * @param conf configuration
    * @return WAL Reader instance
    */
-  public static org.apache.hadoop.hbase.wal.WAL.Reader openReader(Path path, Configuration conf)
-    throws IOException {
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "DCN_NULLPOINTER_EXCEPTION",
+      justification = "HDFS-4380")
+  public static WAL.Reader openReader(Path path, Configuration conf) throws IOException {
     long retryInterval = 2000; // 2 sec
     int maxAttempts = 30;
     int attempt = 0;
diff --git a/hbase-server/src/test/java/org/apache/hadoop/hbase/SingleProcessHBaseCluster.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/SingleProcessHBaseCluster.java
index 5e72464ecb5..92db27fdbe3 100644
--- a/hbase-server/src/test/java/org/apache/hadoop/hbase/SingleProcessHBaseCluster.java
+++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/SingleProcessHBaseCluster.java
@@ -210,8 +210,6 @@ public class SingleProcessHBaseCluster extends HBaseClusterInterface {
       try {
         LOG.info("Hook closing fs=" + this.fs);
         this.fs.close();
-      } catch (NullPointerException npe) {
-        LOG.debug("Need to fix these: " + npe.toString());
       } catch (IOException e) {
         LOG.warn("Running hook", e);
       }
diff --git a/hbase-testing-util/src/main/java/org/apache/hadoop/hbase/MiniHBaseCluster.java b/hbase-testing-util/src/main/java/org/apache/hadoop/hbase/MiniHBaseCluster.java
index 8e66c94e33b..4a98bb31e16 100644
--- a/hbase-testing-util/src/main/java/org/apache/hadoop/hbase/MiniHBaseCluster.java
+++ b/hbase-testing-util/src/main/java/org/apache/hadoop/hbase/MiniHBaseCluster.java
@@ -216,8 +216,6 @@ public class MiniHBaseCluster extends HBaseCluster {
       try {
         LOG.info("Hook closing fs=" + this.fs);
         this.fs.close();
-      } catch (NullPointerException npe) {
-        LOG.debug("Need to fix these: " + npe.toString());
       } catch (IOException e) {
         LOG.warn("Running hook", e);
       }