add spotbugs lint, CI should FAIL.

- add spotbugs-maven-plugin
- use spotbugs-annotations instead of jsr305

pom.xml

@@ -88,6 +88,7 @@
 
 		<kotlin.version>1.3.41</kotlin.version>
 		<kotlin.coroutine.version>1.2.2</kotlin.coroutine.version>
+		<spotbugs.version>3.1.12</spotbugs.version>
 	</properties>
 
 	<dependencies>
@@ -101,10 +102,16 @@
 			<version>3.23.2-GA</version>
 			<optional>true</optional>
 		</dependency>
+		<!--
+			JSR305 is already Dormant status, so SpotBugs does not release jsr305 jar file.
+			Please continue using findbugs’ one.
+			depend on spotbugs-annotations instead.
+			https://spotbugs.readthedocs.io/en/stable/migration.html
+		-->
 		<dependency>
-			<groupId>com.google.code.findbugs</groupId>
-			<artifactId>jsr305</artifactId>
-			<version>3.0.2</version>
+			<groupId>com.github.spotbugs</groupId>
+			<artifactId>spotbugs-annotations</artifactId>
+			<version>${spotbugs.version}</version>
 			<optional>true</optional>
 		</dependency>
 		<!-- Testing frameworks and related dependencies -->
@@ -290,6 +297,16 @@
 					<autoReleaseAfterClose>true</autoReleaseAfterClose>
 				</configuration>
 			</plugin>
+			<!--
+				https://spotbugs.github.io/
+				https://spotbugs.readthedocs.io/en/latest/introduction.html
+				https://spotbugs.readthedocs.io/en/latest/maven.html
+			-->
+			<plugin>
+				<groupId>com.github.spotbugs</groupId>
+				<artifactId>spotbugs-maven-plugin</artifactId>
+				<version>${spotbugs.version}</version>
+			</plugin>
 			<!--
 					official docs: https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html
 
@@ -481,6 +498,31 @@
 				</plugins>
 			</build>
 		</profile>
+		<profile>
+			<id>lint</id>
+			<activation>
+				<property>
+					<name>performRelease</name>
+					<value>true</value>
+				</property>
+			</activation>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>com.github.spotbugs</groupId>
+						<artifactId>spotbugs-maven-plugin</artifactId>
+						<executions>
+							<execution>
+								<phase>test-compile</phase>
+								<goals>
+									<goal>check</goal>
+								</goals>
+							</execution>
+						</executions>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
 		<profile>
 			<id>gen-git-properties</id>
 			<activation>
@@ -495,6 +537,9 @@
 						Maven plugin which includes build-time git repository information into an POJO / *.properties).
 						Make your apps tell you which version exactly they were built from! Priceless in large distributed deployments.
 							https://github.com/ktoso/maven-git-commit-id-plugin
+
+						Spotbugs support @SuppressWarnings
+						https://github.com/spotbugs/spotbugs/issues/737#issuecomment-416118033
 					-->
 					<plugin>
 						<groupId>pl.project13.maven</groupId>

pom4ide.xml

@@ -88,6 +88,7 @@
 
 		<kotlin.version>1.3.41</kotlin.version>
 		<kotlin.coroutine.version>1.2.2</kotlin.coroutine.version>
+		<spotbugs.version>3.1.12</spotbugs.version>
 	</properties>
 
 	<dependencies>
@@ -101,10 +102,16 @@
 			<version>3.23.2-GA</version>
 			<optional>true</optional>
 		</dependency>
+		<!--
+			JSR305 is already Dormant status, so SpotBugs does not release jsr305 jar file.
+			Please continue using findbugs’ one.
+			depend on spotbugs-annotations instead.
+			https://spotbugs.readthedocs.io/en/stable/migration.html
+		-->
 		<dependency>
-			<groupId>com.google.code.findbugs</groupId>
-			<artifactId>jsr305</artifactId>
-			<version>3.0.2</version>
+			<groupId>com.github.spotbugs</groupId>
+			<artifactId>spotbugs-annotations</artifactId>
+			<version>${spotbugs.version}</version>
 			<optional>true</optional>
 		</dependency>
 		<!-- Testing frameworks and related dependencies -->
@@ -290,6 +297,16 @@
 					<autoReleaseAfterClose>true</autoReleaseAfterClose>
 				</configuration>
 			</plugin>
+			<!--
+				https://spotbugs.github.io/
+				https://spotbugs.readthedocs.io/en/latest/introduction.html
+				https://spotbugs.readthedocs.io/en/latest/maven.html
+			-->
+			<plugin>
+				<groupId>com.github.spotbugs</groupId>
+				<artifactId>spotbugs-maven-plugin</artifactId>
+				<version>${spotbugs.version}</version>
+			</plugin>
 			<!--
 					official docs: https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html
 
@@ -481,6 +498,31 @@
 				</plugins>
 			</build>
 		</profile>
+		<profile>
+			<id>lint</id>
+			<activation>
+				<property>
+					<name>performRelease</name>
+					<value>true</value>
+				</property>
+			</activation>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>com.github.spotbugs</groupId>
+						<artifactId>spotbugs-maven-plugin</artifactId>
+						<executions>
+							<execution>
+								<phase>test-compile</phase>
+								<goals>
+									<goal>check</goal>
+								</goals>
+							</execution>
+						</executions>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
 		<profile>
 			<id>gen-git-properties</id>
 			<activation>
@@ -495,6 +537,9 @@
 						Maven plugin which includes build-time git repository information into an POJO / *.properties).
 						Make your apps tell you which version exactly they were built from! Priceless in large distributed deployments.
 							https://github.com/ktoso/maven-git-commit-id-plugin
+
+						Spotbugs support @SuppressWarnings
+						https://github.com/spotbugs/spotbugs/issues/737#issuecomment-416118033
 					-->
 					<plugin>
 						<groupId>pl.project13.maven</groupId>