errorprone cleanliness

[DaanHoogland]

go through the code by instating error prone and fix any issues it reports. Once that epic work is done we can permanently install errorprone as a pre-commit hook.

commit 9f9a2b6b7e094537fea75f633d355f983d4c15d7
Author: Daan Hoogland <daan@onecht.net>
Date:   Thu Jan 12 19:32:35 2023 +0100

    errorprone

diff --git a/pom.xml b/pom.xml
index 204c74cc76..13c46d7521 100644
--- a/pom.xml
+++ b/pom.xml
@@ -817,6 +817,32 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${cs.compiler-plugin.version}</version>
+                <configuration>
+                    <source>8</source>
+                    <target>8</target>
+                    <encoding>UTF-8</encoding>
+                    <compilerArgs>
+                        <arg>-XDcompilePolicy=simple</arg>
+                        <arg>-Xplugin:ErrorProne</arg>
+                    </compilerArgs>
+                    <annotationProcessorPaths>
+                        <path>
+                            <groupId>com.google.errorprone</groupId>
+                            <artifactId>error_prone_core</artifactId>
+                            <version>2.18.0</version>
+                        </path>
+                        <!-- Other annotation processors go here.
+
+                        If 'annotationProcessorPaths' is set, processors will no longer be
+                        discovered on the regular -classpath; see also 'Using Error Prone
+                        together with other annotation processors' below. -->
+                    </annotationProcessorPaths>
+                </configuration>
+            </plugin>
         </plugins>
         <pluginManagement>
             <plugins>
@@ -1074,15 +1100,26 @@
                     <configuration>
                         <source>${cs.jdk.version}</source>
                         <target>${cs.jdk.version}</target>
-                        <fork>true</fork>
-                        <meminitial>128m</meminitial>
-                        <maxmem>512m</maxmem>
+                        <encoding>UTF-8</encoding>
                         <compilerArgs>
                             <arg>-XDignore.symbol.file=true</arg>
                             <arg>--add-opens=java.base/java.lang=ALL-UNNAMED</arg>
                             <arg>--add-exports=java.base/sun.security.x509=ALL-UNNAMED</arg>
                             <arg>--add-exports=java.base/sun.security.provider=ALL-UNNAMED</arg>
+                            <arg>-XDcompilePolicy=simple</arg>
+                            <arg>-Xplugin:ErrorProne</arg>
+                            <arg>--illegal-access=warn</arg>
                         </compilerArgs>
+                        <annotationProcessorPaths>
+                            <path>
+                                <groupId>com.google.errorprone</groupId>
+                                <artifactId>error_prone_core</artifactId>
+                                <version>2.18.0</version>
+                            </path>
+                        </annotationProcessorPaths>
+                        <fork>true</fork>
+                        <meminitial>128m</meminitial>
+                        <maxmem>512m</maxmem>
                     </configuration>
                 </plugin>
                 <plugin>

the above can be added to the main pom.xml and for any issues reported child issues of this or PR can be created directly. The scope of this is would be enormous and too big to deal with at once.