refactor: fixes various code analyser issues (#1118)

* chore: removes final modifier from methods

Removes final modifier from private and static methods.

* chore: adds diamond operator to generic class call

* chore: simplifies boolean expression

* chore: removes redundant throws clauses

* chore: marks ignored exceptions with comments

* chore: anonymous types replaced with lambda calls

* chore: uses comparator combinator

* chore: lambda replaced with method reference

* chore: makes inner class static

* chore: replaces Arrays.asList with emptyList

* chore: removes redundant initializers

* chore: removes redundant toString calls

* chore: explicit type arguments can be inferred

* chore: removes redundant type casts

* chore: replaces StringBuilder with String

* chore: removes redundant suppressions

* chore: list method replaced with value

* chore: uses comparator combinator

* chore: uses singletonList instead of asList

* chore: removes redundant type casts / parameters

* chore: addresses pr comments

* chore: removes unnecessary type cast

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractResultSet.java

@@ -32,7 +32,6 @@
 import com.google.cloud.spanner.spi.v1.SpannerRpc;
 import com.google.cloud.spanner.v1.stub.SpannerStubSettings;
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Function;
 import com.google.common.collect.AbstractIterator;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
@@ -225,7 +224,7 @@ protected com.google.protobuf.Value computeNext() {
                   + newValue.getKindCase());
         }
         if (kind == KindCase.STRING_VALUE) {
-          merged = (String) merged + newValue.getStringValue();
+          merged = merged + newValue.getStringValue();
         } else {
           concatLists(
               (List<com.google.protobuf.Value>) merged, newValue.getListValue().getValuesList());
@@ -319,7 +318,7 @@ private void concatLists(List<com.google.protobuf.Value> a, List<com.google.prot
         KindCase lastKind = last.getKindCase();
         KindCase firstKind = first.getKindCase();
         if (isMergeable(lastKind) && lastKind == firstKind) {
-          com.google.protobuf.Value merged = null;
+          com.google.protobuf.Value merged;
           if (lastKind == KindCase.STRING_VALUE) {
             String lastStr = last.getStringValue();
             String firstStr = first.getStringValue();
@@ -524,12 +523,7 @@ static Object decodeArrayValue(Type elementType, ListValue listValue) {
           // Use a view: element conversion is virtually free.
           return Lists.transform(
               listValue.getValuesList(),
-              new Function<com.google.protobuf.Value, Boolean>() {
-                @Override
-                public Boolean apply(com.google.protobuf.Value input) {
-                  return input.getKindCase() == KindCase.NULL_VALUE ? null : input.getBoolValue();
-                }
-              });
+              input -> input.getKindCase() == KindCase.NULL_VALUE ? null : input.getBoolValue());
         case INT64:
           // For int64/float64 types, use custom containers.  These avoid wrapper object
           // creation for non-null arrays.
@@ -551,12 +545,7 @@ public Boolean apply(com.google.protobuf.Value input) {
         case STRING:
           return Lists.transform(
               listValue.getValuesList(),
-              new Function<com.google.protobuf.Value, String>() {
-                @Override
-                public String apply(com.google.protobuf.Value input) {
-                  return input.getKindCase() == KindCase.NULL_VALUE ? null : input.getStringValue();
-                }
-              });
+              input -> input.getKindCase() == KindCase.NULL_VALUE ? null : input.getStringValue());
         case BYTES:
           {
             // Materialize list: element conversion is expensive and should happen only once.
@@ -1012,12 +1001,9 @@ private static void backoffSleep(Context context, long backoffMillis) throws Spa
               ImmutableMap.of("Delay", AttributeValue.longAttributeValue(backoffMillis)));
       final CountDownLatch latch = new CountDownLatch(1);
       final Context.CancellationListener listener =
-          new Context.CancellationListener() {
-            @Override
-            public void cancelled(Context context) {
-              // Wakeup on cancellation / DEADLINE_EXCEEDED.
-              latch.countDown();
-            }
+          ignored -> {
+            // Wakeup on cancellation / DEADLINE_EXCEEDED.
+            latch.countDown();
           };
 
       context.addListener(listener, DirectExecutor.INSTANCE);

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AsyncResultSetImpl.java

@@ -16,7 +16,6 @@
 
 package com.google.cloud.spanner;
 
-import com.google.api.core.ApiAsyncFunction;
 import com.google.api.core.ApiFuture;
 import com.google.api.core.ApiFutures;
 import com.google.api.core.ListenableFutureToApiFuture;
@@ -529,18 +528,10 @@ public <T> ApiFuture<List<T>> toListAsync(
       Preconditions.checkState(!closed, "This AsyncResultSet has been closed");
       Preconditions.checkState(
           this.state == State.INITIALIZED, "This AsyncResultSet has already been used.");
-      final SettableApiFuture<List<T>> res = SettableApiFuture.<List<T>>create();
+      final SettableApiFuture<List<T>> res = SettableApiFuture.create();
       CreateListCallback<T> callback = new CreateListCallback<>(res, transformer);
       ApiFuture<Void> finished = setCallback(executor, callback);
-      return ApiFutures.transformAsync(
-          finished,
-          new ApiAsyncFunction<Void, List<T>>() {
-            @Override
-            public ApiFuture<List<T>> apply(Void input) throws Exception {
-              return res;
-            }
-          },
-          MoreExecutors.directExecutor());
+      return ApiFutures.transformAsync(finished, ignored -> res, MoreExecutors.directExecutor());
     }
   }
 

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AsyncRunnerImpl.java

@@ -18,7 +18,6 @@
 
 import static com.google.common.base.Preconditions.checkState;
 
-import com.google.api.core.ApiFunction;
 import com.google.api.core.ApiFuture;
 import com.google.api.core.ApiFutures;
 import com.google.api.core.SettableApiFuture;
@@ -79,14 +78,7 @@ private void setCommitResponse() {
   public ApiFuture<Timestamp> getCommitTimestamp() {
     checkState(commitResponse != null, "runAsync() has not yet been called");
     return ApiFutures.transform(
-        commitResponse,
-        new ApiFunction<CommitResponse, Timestamp>() {
-          @Override
-          public Timestamp apply(CommitResponse input) {
-            return input.getCommitTimestamp();
-          }
-        },
-        MoreExecutors.directExecutor());
+        commitResponse, CommitResponse::getCommitTimestamp, MoreExecutors.directExecutor());
   }
 
   public ApiFuture<CommitResponse> getCommitResponse() {

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AsyncTransactionManagerImpl.java

@@ -16,8 +16,6 @@
 
 package com.google.cloud.spanner;
 
-import com.google.api.core.ApiAsyncFunction;
-import com.google.api.core.ApiFunction;
 import com.google.api.core.ApiFuture;
 import com.google.api.core.ApiFutureCallback;
 import com.google.api.core.ApiFutures;
@@ -30,7 +28,6 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Preconditions;
 import com.google.common.util.concurrent.MoreExecutors;
-import com.google.protobuf.Empty;
 import io.opencensus.trace.Span;
 import io.opencensus.trace.Tracer;
 import io.opencensus.trace.Tracing;
@@ -73,7 +70,7 @@ public ApiFuture<Void> closeAsync() {
     if (txn != null) {
       txn.close();
     }
-    return MoreObjects.firstNonNull(res, ApiFutures.<Void>immediateFuture(null));
+    return MoreObjects.firstNonNull(res, ApiFutures.immediateFuture(null));
   }
 
   @Override
@@ -154,14 +151,7 @@ public void onSuccess(CommitResponse result) {
         },
         MoreExecutors.directExecutor());
     return ApiFutures.transform(
-        commitResponseFuture,
-        new ApiFunction<CommitResponse, Timestamp>() {
-          @Override
-          public Timestamp apply(CommitResponse input) {
-            return input.getCommitTimestamp();
-          }
-        },
-        MoreExecutors.directExecutor());
+        commitResponseFuture, CommitResponse::getCommitTimestamp, MoreExecutors.directExecutor());
   }
 
   @Override
@@ -172,12 +162,7 @@ public ApiFuture<Void> rollbackAsync() {
     try {
       return ApiFutures.transformAsync(
           txn.rollbackAsync(),
-          new ApiAsyncFunction<Empty, Void>() {
-            @Override
-            public ApiFuture<Void> apply(Empty input) throws Exception {
-              return ApiFutures.immediateFuture(null);
-            }
-          },
+          ignored -> ApiFutures.immediateFuture(null),
           MoreExecutors.directExecutor());
     } finally {
       txnState = TransactionState.ROLLED_BACK;

google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseAdminClientImpl.java

@@ -16,11 +16,9 @@
 
 package com.google.cloud.spanner;
 
-import com.google.api.core.ApiFunction;
 import com.google.api.gax.grpc.ProtoOperationTransformers;
 import com.google.api.gax.longrunning.OperationFuture;
 import com.google.api.gax.longrunning.OperationFutureImpl;
-import com.google.api.gax.longrunning.OperationSnapshot;
 import com.google.api.gax.paging.Page;
 import com.google.cloud.Policy;
 import com.google.cloud.Policy.DefaultMarshaller;
@@ -108,22 +106,15 @@ public OperationFuture<Database, RestoreDatabaseMetadata> restoreDatabase(Restor
     return new OperationFutureImpl<>(
         rawOperationFuture.getPollingFuture(),
         rawOperationFuture.getInitialFuture(),
-        new ApiFunction<OperationSnapshot, Database>() {
-          @Override
-          public Database apply(OperationSnapshot snapshot) {
-            return Database.fromProto(
+        snapshot ->
+            Database.fromProto(
                 ProtoOperationTransformers.ResponseTransformer.create(
                         com.google.spanner.admin.database.v1.Database.class)
                     .apply(snapshot),
-                DatabaseAdminClientImpl.this);
-          }
-        },
+                DatabaseAdminClientImpl.this),
         ProtoOperationTransformers.MetadataTransformer.create(RestoreDatabaseMetadata.class),
-        new ApiFunction<Exception, Database>() {
-          @Override
-          public Database apply(Exception e) {
-            throw SpannerExceptionFactory.newSpannerException(e);
-          }
+        e -> {
+          throw SpannerExceptionFactory.newSpannerException(e);
         });
   }
 
@@ -154,30 +145,24 @@ public OperationFuture<Backup, CreateBackupMetadata> createBackup(Backup backupI
     return new OperationFutureImpl<>(
         rawOperationFuture.getPollingFuture(),
         rawOperationFuture.getInitialFuture(),
-        new ApiFunction<OperationSnapshot, Backup>() {
-          @Override
-          public Backup apply(OperationSnapshot snapshot) {
-            com.google.spanner.admin.database.v1.Backup proto =
-                ProtoOperationTransformers.ResponseTransformer.create(
-                        com.google.spanner.admin.database.v1.Backup.class)
-                    .apply(snapshot);
-            return Backup.fromProto(
-                com.google.spanner.admin.database.v1.Backup.newBuilder(proto)
-                    .setName(proto.getName())
-                    .setExpireTime(proto.getExpireTime())
-                    .setVersionTime(proto.getVersionTime())
-                    .setState(proto.getState())
-                    .setEncryptionInfo(proto.getEncryptionInfo())
-                    .build(),
-                DatabaseAdminClientImpl.this);
-          }
+        snapshot -> {
+          com.google.spanner.admin.database.v1.Backup proto =
+              ProtoOperationTransformers.ResponseTransformer.create(
+                      com.google.spanner.admin.database.v1.Backup.class)
+                  .apply(snapshot);
+          return Backup.fromProto(
+              com.google.spanner.admin.database.v1.Backup.newBuilder(proto)
+                  .setName(proto.getName())
+                  .setExpireTime(proto.getExpireTime())
+                  .setVersionTime(proto.getVersionTime())
+                  .setState(proto.getState())
+                  .setEncryptionInfo(proto.getEncryptionInfo())
+                  .build(),
+              DatabaseAdminClientImpl.this);
         },
         ProtoOperationTransformers.MetadataTransformer.create(CreateBackupMetadata.class),
-        new ApiFunction<Exception, Backup>() {
-          @Override
-          public Backup apply(Exception e) {
-            throw SpannerExceptionFactory.newSpannerException(e);
-          }
+        e -> {
+          throw SpannerExceptionFactory.newSpannerException(e);
         });
   }
 
@@ -311,22 +296,15 @@ public OperationFuture<Database, CreateDatabaseMetadata> createDatabase(
     return new OperationFutureImpl<>(
         rawOperationFuture.getPollingFuture(),
         rawOperationFuture.getInitialFuture(),
-        new ApiFunction<OperationSnapshot, Database>() {
-          @Override
-          public Database apply(OperationSnapshot snapshot) {
-            return Database.fromProto(
+        snapshot ->
+            Database.fromProto(
                 ProtoOperationTransformers.ResponseTransformer.create(
                         com.google.spanner.admin.database.v1.Database.class)
                     .apply(snapshot),
-                DatabaseAdminClientImpl.this);
-          }
-        },
+                DatabaseAdminClientImpl.this),
         ProtoOperationTransformers.MetadataTransformer.create(CreateDatabaseMetadata.class),
-        new ApiFunction<Exception, Database>() {
-          @Override
-          public Database apply(Exception e) {
-            throw SpannerExceptionFactory.newSpannerException(e);
-          }
+        e -> {
+          throw SpannerExceptionFactory.newSpannerException(e);
         });
   }
 
@@ -350,19 +328,13 @@ public OperationFuture<Void, UpdateDatabaseDdlMetadata> updateDatabaseDdl(
     return new OperationFutureImpl<>(
         rawOperationFuture.getPollingFuture(),
         rawOperationFuture.getInitialFuture(),
-        new ApiFunction<OperationSnapshot, Void>() {
-          @Override
-          public Void apply(OperationSnapshot snapshot) {
-            ProtoOperationTransformers.ResponseTransformer.create(Empty.class).apply(snapshot);
-            return null;
-          }
+        snapshot -> {
+          ProtoOperationTransformers.ResponseTransformer.create(Empty.class).apply(snapshot);
+          return null;
         },
         ProtoOperationTransformers.MetadataTransformer.create(UpdateDatabaseDdlMetadata.class),
-        new ApiFunction<Exception, Void>() {
-          @Override
-          public Void apply(Exception e) {
-            throw SpannerExceptionFactory.newSpannerException(e);
-          }
+        e -> {
+          throw SpannerExceptionFactory.newSpannerException(e);
         });
   }
 

google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseClientImpl.java

@@ -64,13 +64,7 @@ public CommitResponse writeWithOptions(
       throws SpannerException {
     Span span = tracer.spanBuilder(READ_WRITE_TRANSACTION).startSpan();
     try (Scope s = tracer.withSpan(span)) {
-      return runWithSessionRetry(
-          new Function<Session, CommitResponse>() {
-            @Override
-            public CommitResponse apply(Session session) {
-              return session.writeWithOptions(mutations, options);
-            }
-          });
+      return runWithSessionRetry(session -> session.writeWithOptions(mutations, options));
     } catch (RuntimeException e) {
       TraceUtil.setWithFailure(span, e);
       throw e;
@@ -91,12 +85,7 @@ public CommitResponse writeAtLeastOnceWithOptions(
     Span span = tracer.spanBuilder(READ_WRITE_TRANSACTION).startSpan();
     try (Scope s = tracer.withSpan(span)) {
       return runWithSessionRetry(
-          new Function<Session, CommitResponse>() {
-            @Override
-            public CommitResponse apply(Session session) {
-              return session.writeAtLeastOnceWithOptions(mutations, options);
-            }
-          });
+          session -> session.writeAtLeastOnceWithOptions(mutations, options));
     } catch (RuntimeException e) {
       TraceUtil.setWithFailure(span, e);
       throw e;
@@ -221,13 +210,7 @@ public AsyncTransactionManager transactionManagerAsync(TransactionOption... opti
   public long executePartitionedUpdate(final Statement stmt, final UpdateOption... options) {
     Span span = tracer.spanBuilder(PARTITION_DML_TRANSACTION).startSpan();
     try (Scope s = tracer.withSpan(span)) {
-      return runWithSessionRetry(
-          new Function<Session, Long>() {
-            @Override
-            public Long apply(Session session) {
-              return session.executePartitionedUpdate(stmt, options);
-            }
-          });
+      return runWithSessionRetry(session -> session.executePartitionedUpdate(stmt, options));
     } catch (RuntimeException e) {
       TraceUtil.endSpanWithFailure(span, e);
       throw e;