refactor: Remove redundant protected access modifiers and enable the ProtectedMembersInFinalClass ErrorProne check. (#37757)

Author: stankiewicz

buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy

@@ -1559,7 +1559,6 @@ class BeamModulePlugin implements Plugin<Project> {
             "MixedMutabilityReturnType",
             "PreferJavaTimeOverload",
             "NonCanonicalType",
-            "ProtectedMembersInFinalClass",
             "Slf4jFormatShouldBeConst",
             "Slf4jSignOnlyFormat",
             "StaticAssignmentInConstructor",

runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/util/common/worker/CachingShuffleBatchReader.java

@@ -83,8 +83,8 @@ public Batch read(@Nullable ShufflePosition startPosition, @Nullable ShufflePosi
 
   /** The key for the entries stored in the batch cache. */
   static final class BatchRange {
-    protected final @Nullable ShufflePosition startPosition;
-    protected final @Nullable ShufflePosition endPosition;
+    final @Nullable ShufflePosition startPosition;
+    final @Nullable ShufflePosition endPosition;
 
     public BatchRange(
         @Nullable ShufflePosition startPosition, @Nullable ShufflePosition endPosition) {

sdks/java/core/src/main/java/org/apache/beam/sdk/coders/DelegateCoder.java

@@ -176,7 +176,7 @@ private <InputT, OutputT> OutputT applyAndWrapExceptions(
   // to try to deduce a good type descriptor.
   private final @Nullable TypeDescriptor<T> typeDescriptor;
 
-  protected DelegateCoder(
+  DelegateCoder(
       Coder<IntermediateT> coder,
       CodingFunction<T, IntermediateT> toFn,
       CodingFunction<IntermediateT, T> fromFn,

sdks/java/core/src/main/java/org/apache/beam/sdk/coders/StringDelegateCoder.java

@@ -58,7 +58,7 @@ public String toString() {
   private final DelegateCoder<T, String> delegateCoder;
   private final Class<T> clazz;
 
-  protected StringDelegateCoder(final Class<T> clazz, TypeDescriptor<T> typeDescriptor) {
+  StringDelegateCoder(final Class<T> clazz, TypeDescriptor<T> typeDescriptor) {
     delegateCoder =
         DelegateCoder.of(
             StringUtf8Coder.of(),

sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileBasedSink.java

@@ -1177,8 +1177,7 @@ public static final class FileResultCoder<DestinationT>
     private final Coder<BoundedWindow> windowCoder;
     private final Coder<DestinationT> destinationCoder;
 
-    protected FileResultCoder(
-        Coder<BoundedWindow> windowCoder, Coder<DestinationT> destinationCoder) {
+    FileResultCoder(Coder<BoundedWindow> windowCoder, Coder<DestinationT> destinationCoder) {
       this.windowCoder = NullableCoder.of(windowCoder);
       this.destinationCoder = destinationCoder;
     }

sdks/java/io/google-cloud-platform/src/test/java/org/apache/beam/sdk/io/gcp/firestore/PartitionQueryResponseToRunQueryRequestTest.java

@@ -50,7 +50,7 @@
     "initialization.fields.uninitialized") // mockito fields are initialized via the Mockito Runner
 public final class PartitionQueryResponseToRunQueryRequestTest {
 
-  @Mock protected DoFn<PartitionQueryPair, RunQueryRequest>.ProcessContext processContext;
+  @Mock DoFn<PartitionQueryPair, RunQueryRequest>.ProcessContext processContext;
 
   private final StructuredQuery query =
       StructuredQuery.newBuilder()