HDFS-15523. Fix findbugs warnings.

[szetszwo]

See https://issues.apache.org/jira/browse/HDFS-15523

[liuml07]

+1 As long as we do not need the print2File.

If we ditch FileWriter totally one day, we can new PrintWriter(new OutputStreamWriter(new FileOutputStream(f), StandardCharsets.UTF_8), true) to specify the encoding.

[szetszwo]

@liuml07 , Thanks the review and the hint.

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	0m 35s	Docker mode activated.
		_ Prechecks _
+1 💚	dupname	0m 0s	No case conflicting files found.
+1 💚	@author	0m 0s	The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s	The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
		_ trunk Compile Tests _
+1 💚	mvninstall	28m 36s	trunk passed
+1 💚	compile	1m 16s	trunk passed with JDK Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1
+1 💚	compile	1m 9s	trunk passed with JDK Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01
+1 💚	checkstyle	0m 49s	trunk passed
+1 💚	mvnsite	1m 21s	trunk passed
+1 💚	shadedclient	16m 11s	branch has no errors when building and testing our client artifacts.
+1 💚	javadoc	0m 51s	trunk passed with JDK Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1
+1 💚	javadoc	1m 24s	trunk passed with JDK Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01
+0 🆗	spotbugs	3m 2s	Used deprecated FindBugs config; considering switching to SpotBugs.
-1 ❌	findbugs	3m 0s	hadoop-hdfs-project/hadoop-hdfs in trunk has 2 extant findbugs warnings.
		_ Patch Compile Tests _
+1 💚	mvninstall	1m 7s	the patch passed
+1 💚	compile	1m 8s	the patch passed with JDK Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1
+1 💚	javac	1m 8s	the patch passed
+1 💚	compile	0m 59s	the patch passed with JDK Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01
+1 💚	javac	0m 59s	the patch passed
+1 💚	checkstyle	0m 39s	hadoop-hdfs-project/hadoop-hdfs: The patch generated 0 new + 0 unchanged - 2 fixed = 0 total (was 2)
+1 💚	mvnsite	1m 7s	the patch passed
+1 💚	whitespace	0m 0s	The patch has no whitespace issues.
+1 💚	shadedclient	13m 53s	patch has no errors when building and testing our client artifacts.
+1 💚	javadoc	0m 45s	the patch passed with JDK Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1
+1 💚	javadoc	1m 26s	the patch passed with JDK Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01
+1 💚	findbugs	3m 10s	hadoop-hdfs-project/hadoop-hdfs generated 0 new + 0 unchanged - 2 fixed = 0 total (was 2)
		_ Other Tests _
-1 ❌	unit	95m 56s	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 45s	The patch does not generate ASF License warnings.
		178m 5s

Reason	Tests
Failed junit tests	hadoop.hdfs.server.namenode.TestNameNodeRetryCacheMetrics
	hadoop.hdfs.server.sps.TestExternalStoragePolicySatisfier
	hadoop.hdfs.server.namenode.ha.TestBootstrapAliasmap
	hadoop.hdfs.TestMultipleNNPortQOP
	hadoop.fs.contract.hdfs.TestHDFSContractMultipartUploader

Subsystem	Report/Notes
Docker	ClientAPI=1.40 ServerAPI=1.40 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2218/1/artifact/out/Dockerfile
GITHUB PR	#2218
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient findbugs checkstyle
uname	Linux f7001c2e3d56 4.15.0-60-generic #67-Ubuntu SMP Thu Aug 22 16:55:30 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	personality/hadoop.sh
git revision	trunk / 3fd3aeb
Default Java	Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.8+10-post-Ubuntu-0ubuntu118.04.1 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_265-8u265-b01-0ubuntu2~18.04-b01
findbugs	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2218/1/artifact/out/branch-findbugs-hadoop-hdfs-project_hadoop-hdfs-warnings.html
unit	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2218/1/artifact/out/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2218/1/testReport/
Max. process+thread count	4369 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2218/1/console
versions	git=2.17.1 maven=3.6.0 findbugs=4.0.6
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