diff --git a/babel/src/main/codegen/config.fmpp b/babel/src/main/codegen/config.fmpp
index cc96b248b31e..0580a8afe240 100644
--- a/babel/src/main/codegen/config.fmpp
+++ b/babel/src/main/codegen/config.fmpp
@@ -560,7 +560,7 @@ data: {
     createStatementParserMethods: [
       "SqlCreateTable"
     ]
-    
+
     statementParserMethods: [
       "PostgresqlSqlShow()",
       "PostgresqlSqlSetOption()",
@@ -578,9 +578,9 @@ data: {
     ]
 
     # Custom identifier token.
-    # 
-    # PostgreSQL allows letters with diacritical marks and non-Latin letters 
-    # in the beginning of identifier and additionally dollar sign in the rest of identifier. 
+    #
+    # PostgreSQL allows letters with diacritical marks and non-Latin letters
+    # in the beginning of identifier and additionally dollar sign in the rest of identifier.
     # Letters with diacritical marks and non-Latin letters
     # are represented by character codes 128 to 255 (or in octal \200 to \377).
     # See https://learn.microsoft.com/en-gb/office/vba/language/reference/user-interface-help/character-set-128255
@@ -588,7 +588,7 @@ data: {
     #
     # MySQL allows digit in the beginning of identifier
     customIdentifierToken: "< IDENTIFIER: (<LETTER>|<DIGIT>|[\"\\200\"-\"\\377\"]) (<LETTER>|<DIGIT>|<DOLLAR>|[\"\\200\"-\"\\377\"])* >"
-    
+
     # Binary operators initialization.
     # Example: "InfixCast".
     extraBinaryExpressions: [
diff --git a/babel/src/main/codegen/includes/parserPostgresqlImpls.ftl b/babel/src/main/codegen/includes/parserPostgresqlImpls.ftl
index fee70a58d7b8..630e6a29988c 100644
--- a/babel/src/main/codegen/includes/parserPostgresqlImpls.ftl
+++ b/babel/src/main/codegen/includes/parserPostgresqlImpls.ftl
@@ -121,8 +121,8 @@ SqlNode PostgresqlSqlOptionValues():
 {
    e = PostgresqlSqlOptionValue() { s = span(); list = startList(e); }
    ( <COMMA> e = PostgresqlSqlOptionValue() { list.add(e); } )*
-   { 
-      return list.size() > 1 ? new SqlNodeList(list, s.end(this)) : e; 
+   {
+      return list.size() > 1 ? new SqlNodeList(list, s.end(this)) : e;
    }
 }
 
@@ -194,12 +194,12 @@ SqlNode PostgresqlSqlBeginTransactionMode():
 }
 {
     { s = span(); }
-(   
+(
     LOOKAHEAD(2)
-    <READ> 
+    <READ>
     (
-      <WRITE> { m = SqlBegin.TransactionMode.READ_WRITE; } 
-    | 
+      <WRITE> { m = SqlBegin.TransactionMode.READ_WRITE; }
+    |
       <ONLY>  { m = SqlBegin.TransactionMode.READ_ONLY; }
     )
 |
@@ -207,18 +207,18 @@ SqlNode PostgresqlSqlBeginTransactionMode():
 |
     <NOT> <DEFERRABLE> { m = SqlBegin.TransactionMode.NOT_DEFERRABLE; }
 |
-    <ISOLATION> <LEVEL> 
+    <ISOLATION> <LEVEL>
     (
         <SERIALIZABLE> { m = SqlBegin.TransactionMode.ISOLATION_LEVEL_SERIALIZABLE; }
-    | 
+    |
         <REPEATABLE> <READ> { m = SqlBegin.TransactionMode.ISOLATION_LEVEL_REPEATABLE_READ; }
-    | 
-        <READ> 
-        ( 
-          <COMMITTED> { m = SqlBegin.TransactionMode.ISOLATION_LEVEL_READ_COMMITTED; } 
-        | 
+    |
+        <READ>
+        (
+          <COMMITTED> { m = SqlBegin.TransactionMode.ISOLATION_LEVEL_READ_COMMITTED; }
+        |
           <UNCOMMITTED>  { m = SqlBegin.TransactionMode.ISOLATION_LEVEL_READ_UNCOMMITTED; }
-        ) 
+        )
     )
 ) {
     return m.symbol(s.end(this));
@@ -233,13 +233,13 @@ SqlNode PostgresqlSqlCommit():
 }
 {
   { s = span(); }
-  <COMMIT> [ <WORK> | <TRANSACTION> ] [ 
+  <COMMIT> [ <WORK> | <TRANSACTION> ] [
   (
     <AND> <CHAIN> { chain = AndChain.AND_CHAIN; }
   |
     <AND> <NO> <CHAIN>
   )] {
-    final SqlParserPos pos = s.end(this); 
+    final SqlParserPos pos = s.end(this);
     return SqlCommit.OPERATOR.createCall(pos, chain.symbol(pos));
   }
 }
@@ -252,13 +252,13 @@ SqlNode PostgresqlSqlRollback():
 }
 {
   { s = span(); }
-  <ROLLBACK> [ <WORK> | <TRANSACTION> ] [ 
+  <ROLLBACK> [ <WORK> | <TRANSACTION> ] [
   (
     <AND> <CHAIN> { chain = AndChain.AND_CHAIN; }
   |
     <AND> <NO> <CHAIN>
   )] {
-    final SqlParserPos pos = s.end(this); 
+    final SqlParserPos pos = s.end(this);
     return SqlRollback.OPERATOR.createCall(pos, chain.symbol(pos));
   }
 }
diff --git a/core/src/main/codegen/default_config.fmpp b/core/src/main/codegen/default_config.fmpp
index 422926b0ee17..8c6fa484706b 100644
--- a/core/src/main/codegen/default_config.fmpp
+++ b/core/src/main/codegen/default_config.fmpp
@@ -441,11 +441,11 @@ parser: {
   # Example: "parserImpls.ftl".
   implementationFiles: [
   ]
-  
+
   # Custom identifier token.
   # Example: "< IDENTIFIER: (<LETTER>|<DIGIT>)+ >".
   customIdentifierToken: ""
-      
+
   includePosixOperators: false
   includeCompoundIdentifier: true
   includeBraces: true
diff --git a/core/src/main/java/org/apache/calcite/adapter/enumerable/RexImpTable.java b/core/src/main/java/org/apache/calcite/adapter/enumerable/RexImpTable.java
index f709aae70eac..7af554ea8a67 100644
--- a/core/src/main/java/org/apache/calcite/adapter/enumerable/RexImpTable.java
+++ b/core/src/main/java/org/apache/calcite/adapter/enumerable/RexImpTable.java
@@ -1410,7 +1410,7 @@ static class ArgMinMaxImplementor extends StrictAggImplementor {
       final Primitive p = Primitive.of(compType);
       final boolean isMin = info.aggregation().kind == SqlKind.ARG_MIN;
       final Object inf = p == null ? null : (isMin ? p.max : p.min);
-      //acc[1] = isMin ? {max value} : {min value};
+      // acc[1] = isMin ? {max value} : {min value};
       reset.currentBlock().add(
           Expressions.statement(
               Expressions.assign(reset.accumulator().get(1),
@@ -2853,9 +2853,9 @@ private static class UnaryImplementor extends AbstractRexCallImplementor {
       final Expression argValue = argValueList.get(0);
 
       final Expression e;
-      //Special case for implementing unary minus with BigDecimal type
-      //for other data type(except BigDecimal) '-' operator is OK, but for
-      //BigDecimal, we should call negate method of BigDecimal
+      // Special case for implementing unary minus with BigDecimal type
+      // for other data type(except BigDecimal) '-' operator is OK, but for
+      // BigDecimal, we should call negate method of BigDecimal
       if (expressionType == ExpressionType.Negate && argValue.type == BigDecimal.class
           && null != backupMethodName) {
         e = Expressions.call(argValue, backupMethodName);
diff --git a/core/src/main/java/org/apache/calcite/config/CalciteSystemProperty.java b/core/src/main/java/org/apache/calcite/config/CalciteSystemProperty.java
index 4570cccf936a..0e7281f11a7e 100644
--- a/core/src/main/java/org/apache/calcite/config/CalciteSystemProperty.java
+++ b/core/src/main/java/org/apache/calcite/config/CalciteSystemProperty.java
@@ -16,6 +16,8 @@
  */
 package org.apache.calcite.config;
 
+import org.apache.calcite.util.Bug;
+
 import com.google.common.collect.ImmutableSet;
 
 import org.checkerframework.checker.nullness.qual.Nullable;
@@ -437,7 +439,7 @@ private static CalciteSystemProperty<String> stringProperty(
   }
 
   private static <T> T firstNonEmpty(@CheckForNull T t0, T t1) {
-    //Bug.upgrade("remove when 18.0 is the minimum Guava version");
+    Bug.upgrade("remove when 18.0 is the minimum Guava version");
     if (t0 != null) {
       return t0;
     }
diff --git a/core/src/main/java/org/apache/calcite/jdbc/CalciteMetaImpl.java b/core/src/main/java/org/apache/calcite/jdbc/CalciteMetaImpl.java
index cfc606ece848..cd2608381540 100644
--- a/core/src/main/java/org/apache/calcite/jdbc/CalciteMetaImpl.java
+++ b/core/src/main/java/org/apache/calcite/jdbc/CalciteMetaImpl.java
@@ -549,7 +549,7 @@ Enumerable<MetaFunction> functions(final MetaSchema schema_, final String catalo
     return Linq4j.asEnumerable(schema.calciteSchema.getFunctionNames())
         .selectMany(name ->
             Linq4j.asEnumerable(schema.calciteSchema.getFunctions(name, true))
-                //exclude materialized views from the result set
+                // exclude materialized views from the result set
                 .where(fn -> !(fn instanceof MaterializedViewTable.MaterializedViewTableMacro))
                 .select(fnx ->
                     new MetaFunction(
diff --git a/core/src/main/java/org/apache/calcite/plan/Strong.java b/core/src/main/java/org/apache/calcite/plan/Strong.java
index c0d5cece4c66..3771c21b0780 100644
--- a/core/src/main/java/org/apache/calcite/plan/Strong.java
+++ b/core/src/main/java/org/apache/calcite/plan/Strong.java
@@ -165,7 +165,7 @@ public static boolean allStrong(List<RexNode> operands) {
    * (equivalently, will definitely return null or false). */
   public boolean isNotTrue(RexNode node) {
     switch (node.getKind()) {
-    //TODO Enrich with more possible cases?
+    // TODO Enrich with more possible cases?
     case IS_NOT_NULL:
       return isNull(((RexCall) node).getOperands().get(0));
     case OR:
diff --git a/core/src/main/java/org/apache/calcite/rel/metadata/ReflectiveRelMetadataProvider.java b/core/src/main/java/org/apache/calcite/rel/metadata/ReflectiveRelMetadataProvider.java
index cb775d8380b0..408a53687e67 100644
--- a/core/src/main/java/org/apache/calcite/rel/metadata/ReflectiveRelMetadataProvider.java
+++ b/core/src/main/java/org/apache/calcite/rel/metadata/ReflectiveRelMetadataProvider.java
@@ -124,13 +124,16 @@ public static RelMetadataProvider reflectiveSource(Method method,
   @Deprecated // to be removed before 2.0
   public static RelMetadataProvider reflectiveSource(MetadataHandler target,
       Method... methods) {
-    return reflectiveSource(target, ImmutableList.copyOf(methods), target.getDef().handlerClass);
+    return reflectiveSource(target, ImmutableList.copyOf(methods),
+        target.getDef().handlerClass);
   }
 
   @SuppressWarnings("deprecation")
   public static <M extends Metadata> RelMetadataProvider reflectiveSource(
-      MetadataHandler<? extends M> handler, Class<? extends MetadataHandler<M>> handlerClass) {
-    //When deprecated code is removed, handler.getDef().methods will no longer be required
+      MetadataHandler<? extends M> handler,
+      Class<? extends MetadataHandler<M>> handlerClass) {
+    // When deprecated code is removed, handler.getDef().methods will
+    // no longer be required
     return reflectiveSource(handler, handler.getDef().methods, handlerClass);
   }
 
diff --git a/core/src/main/java/org/apache/calcite/rel/metadata/janino/CacheGeneratorUtil.java b/core/src/main/java/org/apache/calcite/rel/metadata/janino/CacheGeneratorUtil.java
index 939ad2ce1527..4d2e3fa13f15 100644
--- a/core/src/main/java/org/apache/calcite/rel/metadata/janino/CacheGeneratorUtil.java
+++ b/core/src/main/java/org/apache/calcite/rel/metadata/janino/CacheGeneratorUtil.java
@@ -209,7 +209,7 @@ private enum CacheKeyStrategy {
 
       /** Returns e.g. ", ignoreNulls". */
       private StringBuilder safeArgList(StringBuilder buff, Method method) {
-        //We ignore the first 2 arguments since they are included other ways.
+        // We ignore the first 2 arguments since they are included other ways.
         for (Ord<Class<?>> t : Ord.zip(method.getParameterTypes())
             .subList(2, method.getParameterCount())) {
           if (Primitive.is(t.e) || RexNode.class.isAssignableFrom(t.e)) {
diff --git a/core/src/main/java/org/apache/calcite/rel/metadata/janino/RelMetadataHandlerGeneratorUtil.java b/core/src/main/java/org/apache/calcite/rel/metadata/janino/RelMetadataHandlerGeneratorUtil.java
index 1d3ef55836ff..0fd6103cfd0f 100644
--- a/core/src/main/java/org/apache/calcite/rel/metadata/janino/RelMetadataHandlerGeneratorUtil.java
+++ b/core/src/main/java/org/apache/calcite/rel/metadata/janino/RelMetadataHandlerGeneratorUtil.java
@@ -81,7 +81,7 @@ public static HandlerNameAndGeneratedCode generateHandler(
     buff.append("public final class ").append(name).append("\n")
         .append("  implements ").append(handlerClass.getCanonicalName()).append(" {\n");
 
-    // PROPERTIES
+    // Properties
     Ord.forEach(declaredMethods.values(), (declaredMethod, i) ->
         CacheGeneratorUtil.cacheProperties(buff, declaredMethod, i));
     for (Map.Entry<MetadataHandler<?>, String> handlerAndName : handlerToName.entrySet()) {
@@ -89,7 +89,7 @@ public static HandlerNameAndGeneratedCode generateHandler(
           .append(' ').append(handlerAndName.getValue()).append(";\n");
     }
 
-    // CONSTRUCTOR
+    // Constructor
     buff.append("  public ").append(name).append("(\n");
     for (Map.Entry<MetadataHandler<?>, String> handlerAndName : handlerToName.entrySet()) {
       buff.append("      ")
@@ -108,7 +108,7 @@ public static HandlerNameAndGeneratedCode generateHandler(
     }
     buff.append("  }\n");
 
-    // METHODS
+    // Methods
     getDefMethod(buff,
         handlerToName.values()
             .stream()
@@ -145,8 +145,8 @@ private static void getDefMethod(StringBuilder buff, @Nullable String handlerNam
 
   private static String simpleNameForHandler(Class<? extends MetadataHandler<?>> clazz) {
     String simpleName = clazz.getSimpleName();
-    // Previously the pattern was to have a nested in class named Handler
-    // So we need to add the parents class to get a unique name
+    // Previously the pattern was to have a nested in class named Handler.
+    // So we need to add the parents class to get a unique name.
     if (simpleName.equals("Handler")) {
       String[] parts = clazz.getName().split("[.$]");
       return parts[parts.length - 2] + parts[parts.length - 1];
diff --git a/core/src/main/java/org/apache/calcite/rex/package-info.java b/core/src/main/java/org/apache/calcite/rex/package-info.java
index 351f21ce4752..4467d8c65ca7 100644
--- a/core/src/main/java/org/apache/calcite/rex/package-info.java
+++ b/core/src/main/java/org/apache/calcite/rex/package-info.java
@@ -33,7 +33,6 @@
  *
  * <h2>Expressions</h2>
  *
- *
  * <p>Every row-expression has a type. (Compare with
  * {@link org.apache.calcite.sql.SqlNode}, which is created before validation,
  * and therefore types may not be available.)
diff --git a/core/src/main/java/org/apache/calcite/runtime/JsonFunctions.java b/core/src/main/java/org/apache/calcite/runtime/JsonFunctions.java
index 348938db2fd0..c65f70c1f61f 100644
--- a/core/src/main/java/org/apache/calcite/runtime/JsonFunctions.java
+++ b/core/src/main/java/org/apache/calcite/runtime/JsonFunctions.java
@@ -721,10 +721,11 @@ private static void insertToJson(DocumentContext ctx, String path, Object value)
     final String parentPath;
     final String key;
 
-    //The following paragraph of logic is mainly used to obtain the parent node path of path and
-    //the key value that should be inserted when the preant Path is map.
-    //eg: path is $.a ,parentPath is $
-    //eg: path is $.a[1] ,parentPath is $.a
+    // The following paragraph of logic is mainly used to obtain the
+    // parent node path of path and the key value that should be
+    // inserted when the preant Path is map.
+    // eg: path is $.a ,parentPath is $
+    // eg: path is $.a[1] ,parentPath is $.a
     Integer dotIndex = path.lastIndexOf(".");
     Integer leftBracketIndex = path.lastIndexOf("[");
     if (dotIndex.equals(-1) && leftBracketIndex.equals(-1)) {
diff --git a/core/src/main/java/org/apache/calcite/sql/SqlDialect.java b/core/src/main/java/org/apache/calcite/sql/SqlDialect.java
index 53a57eab947b..ae07d64cf2e8 100644
--- a/core/src/main/java/org/apache/calcite/sql/SqlDialect.java
+++ b/core/src/main/java/org/apache/calcite/sql/SqlDialect.java
@@ -479,8 +479,8 @@ public void unparseSqlDatetimeArithmetic(SqlWriter writer,
     writer.sep((SqlKind.PLUS == sqlKind) ? "+" : "-");
     call.operand(1).unparse(writer, leftPrec, rightPrec);
     writer.endList(frame);
-    //Only two parameters are present normally
-    //Checking parameter count to prevent errors
+    // Only two parameters are present normally.
+    // Checking parameter count to prevent errors.
     if (call.getOperandList().size() > 2) {
       call.operand(2).unparse(writer, leftPrec, rightPrec);
     }
diff --git a/core/src/main/java/org/apache/calcite/sql/dialect/MssqlSqlDialect.java b/core/src/main/java/org/apache/calcite/sql/dialect/MssqlSqlDialect.java
index 6f76207b0cad..0867133956b0 100644
--- a/core/src/main/java/org/apache/calcite/sql/dialect/MssqlSqlDialect.java
+++ b/core/src/main/java/org/apache/calcite/sql/dialect/MssqlSqlDialect.java
@@ -225,7 +225,7 @@ private static void unparseFloor(SqlWriter writer, SqlCall call) {
     final SqlWriter.Frame frame = writer.startFunCall("DATEADD");
     SqlNode operand = call.operand(1);
     if (operand instanceof SqlIntervalLiteral) {
-      //There is no DATESUB method available, so change the sign.
+      // There is no DATESUB method available, so change the sign.
       unparseSqlIntervalLiteralMssql(
           writer, (SqlIntervalLiteral) operand, sqlKind == SqlKind.MINUS ? -1 : 1);
     } else {
diff --git a/core/src/main/java/org/apache/calcite/sql/type/InferTypes.java b/core/src/main/java/org/apache/calcite/sql/type/InferTypes.java
index 0d340cc1c7d2..1a0cb0dc8623 100644
--- a/core/src/main/java/org/apache/calcite/sql/type/InferTypes.java
+++ b/core/src/main/java/org/apache/calcite/sql/type/InferTypes.java
@@ -54,7 +54,7 @@ private InferTypes() {}
         // because SqlAdvisorValidator produces
         // unknown types for incomplete expressions.
         // Maybe we need to distinguish the two kinds of unknown.
-        //assert !knownType.equals(unknownType);
+        //   assert !knownType.equals(unknownType);
         Arrays.fill(operandTypes, knownType);
       };
 
diff --git a/core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java b/core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java
index e416f6abbdc7..1ab8010d7441 100644
--- a/core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java
+++ b/core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java
@@ -2084,7 +2084,8 @@ private static class TimestampSubConvertlet implements SqlRexConvertlet {
       final TimeUnit unit = first(timeFrame.unit(), TimeUnit.EPOCH);
       final RexNode interval2Sub;
       switch (unit) {
-      //Fractional second units are converted to seconds using their associated multiplier.
+      // Fractional second units are converted to seconds using their
+      // associated multiplier.
       case MICROSECOND:
       case NANOSECOND:
         interval2Sub =
diff --git a/core/src/main/java/org/apache/calcite/util/Bug.java b/core/src/main/java/org/apache/calcite/util/Bug.java
index 1ca3a41fb63e..b2f14d76efe8 100644
--- a/core/src/main/java/org/apache/calcite/util/Bug.java
+++ b/core/src/main/java/org/apache/calcite/util/Bug.java
@@ -40,6 +40,9 @@
  * usages of it. Also, the constant helps track the propagation of the fix: as
  * the fix is integrated into other branches, the constant will be removed from
  * those branches.
+ *
+ * <p>This class depends on no other classes.
+ * (In the past, a dependency on {@code Util} caused class-loading cycles.)
  */
 public abstract class Bug {
   //~ Static fields/initializers ---------------------------------------------
@@ -237,9 +240,8 @@ public static <T> T remark(T remark) {
    * instead using a {@link Deprecated} annotation followed by a comment such as
    * "to be removed before 2.0".
    */
+  @SuppressWarnings("unused")
   public static boolean upgrade(String remark) {
-    Util.discard(remark);
     return false;
   }
-
 }
diff --git a/core/src/main/java/org/apache/calcite/util/Permutation.java b/core/src/main/java/org/apache/calcite/util/Permutation.java
index b7ddf3b217e5..fd187ce23ec6 100644
--- a/core/src/main/java/org/apache/calcite/util/Permutation.java
+++ b/core/src/main/java/org/apache/calcite/util/Permutation.java
@@ -433,8 +433,6 @@ private void setInternal(int source, int target) {
   /**
    * Checks whether this permutation is valid.
    *
-   *
-   *
    * @param fail Whether to assert if invalid
    * @return Whether valid
    */
diff --git a/core/src/main/resources/org/apache/calcite/plan/visualizer/viz-template.html b/core/src/main/resources/org/apache/calcite/plan/visualizer/viz-template.html
index dfaf6aef1d31..0e8ee30553f2 100644
--- a/core/src/main/resources/org/apache/calcite/plan/visualizer/viz-template.html
+++ b/core/src/main/resources/org/apache/calcite/plan/visualizer/viz-template.html
@@ -190,14 +190,14 @@
      */
 
     var updateLocation = () => {
-        var urlParams = new URLSearchParams(location.search); 
+        var urlParams = new URLSearchParams(location.search);
         urlParams.set("step", currentStepIndex);
         urlParams.set("dir", currentRankDirIdx);
         window.history.pushState({}, "", "?" + urlParams.toString());
     };
 
     var parseLocation = () => {
-        var urlParams = new URLSearchParams(location.search); 
+        var urlParams = new URLSearchParams(location.search);
         if (urlParams.has("step")) {
             var stepIdx = Number(urlParams.get("step"))
             if (Number.isInteger(stepIdx))
@@ -309,7 +309,7 @@
                 g.setParent(nodeID, n.set);
 
                 // create links
-                if(n.inputs) 
+                if(n.inputs)
                 for(var inputID of n.inputs) {
                     var input = state.nodes[inputID];
                     var edgeOptions = { arrowheadStyle: "normal" };
@@ -405,14 +405,14 @@
 
     document.getElementById("toggle-list-button").addEventListener("click", () => {
         var col1 = document.getElementById("step-list-column");
-        if (col1.style.display === "none") 
+        if (col1.style.display === "none")
             col1.style.display = "";
-        else 
+        else
             col1.style.display = "none";
     });
 
     // render initial state
-    
+
     parseLocation();
     setCurrentStep(currentStepIndex);
     fitContent();
diff --git a/core/src/test/java/org/apache/calcite/test/JdbcTest.java b/core/src/test/java/org/apache/calcite/test/JdbcTest.java
index 2367c88699dd..b6d7093740ac 100644
--- a/core/src/test/java/org/apache/calcite/test/JdbcTest.java
+++ b/core/src/test/java/org/apache/calcite/test/JdbcTest.java
@@ -6417,7 +6417,7 @@ private void checkGetTimestamp(Connection con) throws SQLException {
     Statement statement = con.createStatement();
 
     // Not supported yet. We set timezone using connect-string parameters.
-    //statement.executeUpdate("alter session set timezone = 'gmt-3'");
+    //   statement.executeUpdate("alter session set timezone = 'gmt-3'");
 
     ResultSet rs = statement.executeQuery("SELECT * FROM (VALUES(\n"
         + " TIMESTAMP '1970-01-01 00:00:00',\n"
diff --git a/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java b/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java
index 1c615186a243..5eebc5410c04 100644
--- a/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java
+++ b/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java
@@ -122,8 +122,10 @@ public class RexImplicationCheckerTest {
     final RexNode bEqTrue = f.eq(f.bl, f.rexBuilder.makeLiteral(true));
     final RexNode bEqFalse = f.eq(f.bl, f.rexBuilder.makeLiteral(false));
 
-    // TODO: Need to support false => true
-    //f.checkImplies(bEqFalse, bEqTrue);
+    if (false) {
+      // TODO: Need to support false => true
+      f.checkImplies(bEqFalse, bEqTrue);
+    }
     f.checkNotImplies(bEqTrue, bEqFalse);
   }
 
@@ -257,7 +259,9 @@ public class RexImplicationCheckerTest {
     final RexNode yGt2AndZGt4 = f.and(yGt2, zGt4);
     final RexNode yGt3AndZGt5 = f.and(yGt3, zGt5);
     final RexNode or = f.or(xGt1, yGt2AndZGt4);
-    //f.checkNotImplies(or, yGt3AndZGt5);
+    if (false) {
+      f.checkNotImplies(or, yGt3AndZGt5);
+    }
     f.checkImplies(yGt3AndZGt5, or);
   }
 
diff --git a/core/src/test/java/org/apache/calcite/test/concurrent/package-info.java b/core/src/test/java/org/apache/calcite/test/concurrent/package-info.java
index 524e6d6d935e..dfc567c9c739 100644
--- a/core/src/test/java/org/apache/calcite/test/concurrent/package-info.java
+++ b/core/src/test/java/org/apache/calcite/test/concurrent/package-info.java
@@ -87,7 +87,6 @@
  * <p>The directive &#64;disable means "skip this script". The deault is the
  * antonym &#64;enable.
  *
- *
  * <h3>Error handling:</h3>
  *
  * <p>When a sql command fails, the rest of its section is skipped. However, if
@@ -207,7 +206,6 @@
  *     VAR=VALUE : binds the script variable VAR to the VALUE; VAR must be
  *     declared at the beginning of the script(s) in a &#64;var command.
  *
- *
  * <h3>Example Script</h3>
  *
  * <blockquote><pre>-- redundant:
diff --git a/core/src/test/java/org/apache/calcite/util/UtilTest.java b/core/src/test/java/org/apache/calcite/util/UtilTest.java
index d5cdff4c3463..cd002ccb7370 100644
--- a/core/src/test/java/org/apache/calcite/util/UtilTest.java
+++ b/core/src/test/java/org/apache/calcite/util/UtilTest.java
@@ -2967,7 +2967,7 @@ private void checkNameMultimap(String s, NameMultimap<Integer> map) {
     assertThat(describe(isLinux("X")), is("is \"X\""));
     assertThat(Unsafe.matches(isLinux("x\ny"), "x\ny"), is(true));
     assertThat(Unsafe.matches(isLinux("x\ny"), "x\r\ny"), is(true));
-    //\n\r is not a valid windows line ending
+    // "\n\r" is not a valid windows line ending
     assertThat(Unsafe.matches(isLinux("x\ny"), "x\n\ry"), is(false));
     assertThat(Unsafe.matches(isLinux("x\ny"), "x\n\ryz"), is(false));
     // left-hand side must be linux or will never match
diff --git a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidExpressions.java b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidExpressions.java
index cf0eea0187d5..5c9902c97dc8 100644
--- a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidExpressions.java
+++ b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidExpressions.java
@@ -123,7 +123,7 @@ private DruidExpressions() {
       final DruidSqlOperatorConverter conversion = druidRel.getOperatorConversionMap()
           .get(operator);
       if (conversion == null) {
-        //unknown operator can not translate
+        // unknown operator; can not translate
         return null;
       } else {
         return conversion.toDruidExpression(rexNode, inputRowType, druidRel);
@@ -132,7 +132,8 @@ private DruidExpressions() {
     if (kind == SqlKind.LITERAL) {
       // Translate literal.
       if (RexLiteral.isNullLiteral(rexNode)) {
-        //case the filter/project might yield to unknown let Calcite deal with this for now
+        // case the filter/project might yield to unknown; let Calcite
+        // deal with this for now
         return null;
       } else if (SqlTypeName.NUMERIC_TYPES.contains(sqlTypeName)) {
         return DruidExpressions.numberLiteral((Number) RexLiteral
diff --git a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidJsonFilter.java b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidJsonFilter.java
index 81cb0ad49c4a..7a1ffc4084ee 100644
--- a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidJsonFilter.java
+++ b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidJsonFilter.java
@@ -108,7 +108,7 @@ abstract class DruidJsonFilter implements DruidJson {
     }
     final DruidJsonFilter partialFilter;
     if (isNumeric) {
-      //need bound filter since it one of operands is numeric
+      // need bound filter since it one of operands is numeric
       partialFilter =
           new JsonBound(columnName, literalValue, false, literalValue,
               false, true, extractionFunction);
diff --git a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java
index 2550aa03c8cf..49b55feba77b 100644
--- a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java
+++ b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java
@@ -851,7 +851,8 @@ protected CalciteConnectionConfig getConnectionConfig() {
       } else if (druidColumn.left != null && druidColumn.right != null) {
        // CASE it is an extraction Dimension
         final String columnPrefix;
-        //@TODO Remove it! if else statement is not really needed it is here to make tests pass.
+        // TODO Remove it! if else statement is not really needed it
+        // is here to make tests pass.
         if (project.getKind() == SqlKind.EXTRACT) {
           columnPrefix =
               EXTRACT_COLUMN_NAME_PREFIX + "_" + requireNonNull(DruidDateTimeUtils
diff --git a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidSqlCastConverter.java b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidSqlCastConverter.java
index e615e44b0541..2aa8bf76921c 100644
--- a/druid/src/main/java/org/apache/calcite/adapter/druid/DruidSqlCastConverter.java
+++ b/druid/src/main/java/org/apache/calcite/adapter/druid/DruidSqlCastConverter.java
@@ -64,13 +64,13 @@ public class DruidSqlCastConverter implements DruidSqlOperatorConverter {
 
     if (SqlTypeName.CHAR_TYPES.contains(fromType)
         && SqlTypeName.DATETIME_TYPES.contains(toType)) {
-      //case chars to dates
+      // case chars to dates
       return castCharToDateTime(toType == SqlTypeName.TIMESTAMP_WITH_LOCAL_TIME_ZONE
               ? timeZone : DateTimeUtils.UTC_ZONE,
           operandExpression, toType, fromTypeString);
     } else if (SqlTypeName.DATETIME_TYPES.contains(fromType)
         && SqlTypeName.CHAR_TYPES.contains(toType)) {
-      //case dates to chars
+      // case dates to chars
       return castDateTimeToChar(fromType == SqlTypeName.TIMESTAMP_WITH_LOCAL_TIME_ZONE
           ? timeZone : DateTimeUtils.UTC_ZONE, operandExpression, fromType);
     } else if (SqlTypeName.DATETIME_TYPES.contains(fromType)
diff --git a/druid/src/main/java/org/apache/calcite/adapter/druid/SubstringOperatorConversion.java b/druid/src/main/java/org/apache/calcite/adapter/druid/SubstringOperatorConversion.java
index 868ec2b782f0..1675bddd79ba 100644
--- a/druid/src/main/java/org/apache/calcite/adapter/druid/SubstringOperatorConversion.java
+++ b/druid/src/main/java/org/apache/calcite/adapter/druid/SubstringOperatorConversion.java
@@ -63,7 +63,7 @@ public class SubstringOperatorConversion implements DruidSqlOperatorConverter {
     }
 
     if (call.getOperands().size() > 2) {
-      //case substring from start index with length
+      // case substring from start index with length
       if (!call.getOperands().get(2).isA(SqlKind.LITERAL)) {
         // case it is an expression try to parse it
         length =
@@ -80,7 +80,7 @@ public class SubstringOperatorConversion implements DruidSqlOperatorConverter {
       }
 
     } else {
-      //case substring from index to the end
+      // case substring from index to the end
       length = DruidExpressions.numberLiteral(-1);
     }
     return DruidQuery.format("substring(%s, %s, %s)", arg, startIndex, length);
diff --git a/druid/src/test/java/org/apache/calcite/test/DruidAdapter2IT.java b/druid/src/test/java/org/apache/calcite/test/DruidAdapter2IT.java
index b57664f462b2..4beddd31ee60 100644
--- a/druid/src/test/java/org/apache/calcite/test/DruidAdapter2IT.java
+++ b/druid/src/test/java/org/apache/calcite/test/DruidAdapter2IT.java
@@ -2003,7 +2003,7 @@ private void checkGroupBySingleSortLimit(boolean approx) {
     sql(sqlQuery)
         .explainContains(plan)
         .throws_("Server returned HTTP response code: 500");
-    //@TODO It seems like calcite is not handling 500 error,
+    // TODO It seems like calcite is not handling 500 error,
     // need to catch it and parse exception message from druid,
     // e.g., throws_("/ by zero");
   }
diff --git a/druid/src/test/java/org/apache/calcite/test/DruidAdapterIT.java b/druid/src/test/java/org/apache/calcite/test/DruidAdapterIT.java
index 9c22e3652cfb..b03f3e19e86a 100644
--- a/druid/src/test/java/org/apache/calcite/test/DruidAdapterIT.java
+++ b/druid/src/test/java/org/apache/calcite/test/DruidAdapterIT.java
@@ -2310,7 +2310,7 @@ private void checkGroupBySingleSortLimit(boolean approx) {
     sql(sqlQuery, FOODMART)
         .explainContains(plan)
         .throws_("Server returned HTTP response code: 500");
-    //@TODO It seems like calcite is not handling 500 error,
+    // TODO It seems like calcite is not handling 500 error,
     // need to catch it and parse exception message from druid,
     // e.g., throws_("/ by zero");
   }
diff --git a/file/src/main/java/org/apache/calcite/adapter/file/FileReader.java b/file/src/main/java/org/apache/calcite/adapter/file/FileReader.java
index 438044f6bd8b..ffa53bc76094 100644
--- a/file/src/main/java/org/apache/calcite/adapter/file/FileReader.java
+++ b/file/src/main/java/org/apache/calcite/adapter/file/FileReader.java
@@ -161,8 +161,7 @@ Elements getHeadings() throws FileReaderException {
 
     // if we haven't cached the headings, get them
     // TODO: this needs to be reworked to properly cache the headings
-    //if (this.headings == null) {
-    if (true) {
+    if (/* this.headings == null */ true) {
       // first row must contain headings
       Elements headings = iterator.next("th");
       // if not, generate some default column names
diff --git a/file/src/main/java/org/apache/calcite/adapter/file/FileRowConverter.java b/file/src/main/java/org/apache/calcite/adapter/file/FileRowConverter.java
index 77995f567648..d6a0d880a2bd 100644
--- a/file/src/main/java/org/apache/calcite/adapter/file/FileRowConverter.java
+++ b/file/src/main/java/org/apache/calcite/adapter/file/FileRowConverter.java
@@ -259,7 +259,7 @@ String read(Element cell) {
             .get(this.selectedElement).ownText());
       } else {
         for (Element child : cell.select(this.selector)) {
-          //String tagName = child.tag().getName();
+          // String tagName = child.tag().getName();
           cellText.add(child.ownText());
         }
       }
diff --git a/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaMessageEnumerator.java b/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaMessageEnumerator.java
index af091a58d3ae..adfd999bdfa3 100644
--- a/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaMessageEnumerator.java
+++ b/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaMessageEnumerator.java
@@ -46,7 +46,7 @@ public class KafkaMessageEnumerator<K, V> implements Enumerator<@Nullable Object
   final KafkaRowConverter<K, V> rowConverter;
   private final AtomicBoolean cancelFlag;
 
-  //runtime
+  // runtime
   private final Deque<ConsumerRecord<K, V>> bufferedRecords = new ArrayDeque<>();
   private @Nullable ConsumerRecord<K, V> curRecord;
 
diff --git a/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaStreamTable.java b/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaStreamTable.java
index ea5f257bcb0d..e432eb803940 100644
--- a/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaStreamTable.java
+++ b/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaStreamTable.java
@@ -70,7 +70,7 @@ public class KafkaStreamTable implements ScannableTable, StreamableTable {
         Properties consumerConfig = new Properties();
         consumerConfig.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,
             tableOptions.getBootstrapServers());
-        //by default it's <byte[], byte[]>
+        // by default it's <byte[], byte[]>
         consumerConfig.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,
             "org.apache.kafka.common.serialization.ByteArrayDeserializer");
         consumerConfig.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG,
diff --git a/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaTableOptions.java b/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaTableOptions.java
index 125a9f139413..f54e7831509a 100644
--- a/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaTableOptions.java
+++ b/kafka/src/main/java/org/apache/calcite/adapter/kafka/KafkaTableOptions.java
@@ -28,7 +28,7 @@ public final class KafkaTableOptions {
   private String topicName;
   private KafkaRowConverter rowConverter;
   private Map<String, String> consumerParams;
-  //added to inject MockConsumer for testing.
+  // added to inject MockConsumer for testing.
   private Consumer consumer;
 
   public String getBootstrapServers() {
diff --git a/linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java b/linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java
index 8494dd531da3..d623d8619d4e 100644
--- a/linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java
+++ b/linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java
@@ -1461,7 +1461,7 @@ private static <TSource, TInner, TKey, TResult> Enumerable<TResult> hashJoinWith
                   innerEnumerable = null;
                 } else {
                   innerEnumerable = innerLookup.get(outerKey);
-                  //apply predicate to filter per-row
+                  // apply predicate to filter per-row
                   if (innerEnumerable != null) {
                     final List<TInner> matchedInners = new ArrayList<>();
                     try (Enumerator<TInner> innerEnumerator =
diff --git a/linq4j/src/main/java/org/apache/calcite/linq4j/tree/DeterministicCodeOptimizer.java b/linq4j/src/main/java/org/apache/calcite/linq4j/tree/DeterministicCodeOptimizer.java
index 7d0dbed8e4ff..453fa69addec 100644
--- a/linq4j/src/main/java/org/apache/calcite/linq4j/tree/DeterministicCodeOptimizer.java
+++ b/linq4j/src/main/java/org/apache/calcite/linq4j/tree/DeterministicCodeOptimizer.java
@@ -320,7 +320,6 @@ protected boolean isMethodDeterministic(Method method) {
    * Checks if new instance creation can be reused. For instance {@code new
    * BigInteger("42")} is effectively final and can be reused.
    *
-   *
    * @param newExpression method to test
    * @return true when the method is deterministic
    */
diff --git a/linq4j/src/main/java/org/apache/calcite/linq4j/tree/Expressions.java b/linq4j/src/main/java/org/apache/calcite/linq4j/tree/Expressions.java
index 79fa310e19db..5f0b87f9e089 100644
--- a/linq4j/src/main/java/org/apache/calcite/linq4j/tree/Expressions.java
+++ b/linq4j/src/main/java/org/apache/calcite/linq4j/tree/Expressions.java
@@ -1902,7 +1902,7 @@ public static UnaryExpression negateChecked(Expression expression) {
   public static UnaryExpression negateChecked(Expression expression,
       Method method) {
     throw new UnsupportedOperationException("not implemented");
-    //return makeUnary(ExpressionType.NegateChecked, expression, null, method);
+    // return makeUnary(ExpressionType.NegateChecked, expression, null, method);
   }
 
   /**
diff --git a/redis/src/test/java/org/apache/calcite/adapter/redis/RedisDataCaseBase.java b/redis/src/test/java/org/apache/calcite/adapter/redis/RedisDataCaseBase.java
index eb9923d46578..e675f6f84b93 100644
--- a/redis/src/test/java/org/apache/calcite/adapter/redis/RedisDataCaseBase.java
+++ b/redis/src/test/java/org/apache/calcite/adapter/redis/RedisDataCaseBase.java
@@ -58,16 +58,16 @@ public void setUp() {
   public void makeData() {
     try (Jedis jedis = pool.getResource()) {
       jedis.del(tableNames);
-      //set string
+      // set string
       jedis.set("raw_01", "123");
       jedis.set("json_01", "{\"DEPTNO\":10,\"NAME\":\"Sales\"}");
       jedis.set("csv_01", "10:Sales");
-      //set list
+      // set list
       jedis.lpush("raw_02", "book1", "book2");
       jedis.lpush("json_02", "{\"DEPTNO\":10,\"NAME\":\"Sales1\"}", "{\"DEPTNO\":20,"
           + "\"NAME\":\"Sales2\"}");
       jedis.lpush("csv_02", "10:Sales", "20:Sales");
-      //set Set
+      // set Set
       jedis.sadd("raw_03", "user1", "user2");
       jedis.sadd("json_03", "{\"DEPTNO\":10,\"NAME\":\"Sales1\"}", "{\"DEPTNO\":20,"
           + "\"NAME\":\"Sales1\"}");
@@ -79,7 +79,7 @@ public void makeData() {
       jedis.zadd("json_04", 2, "{\"DEPTNO\":11,\"NAME\":\"Sales2\"}");
       jedis.zadd("csv_04", 1, "10:Sales");
       jedis.zadd("csv_04", 2, "20:Sales");
-      //set map
+      // set map
       Map<String, String> raw_05 = new HashMap<>();
       raw_05.put("stuA", "a1");
       raw_05.put("stuB", "b2");
diff --git a/redis/src/test/java/org/apache/calcite/adapter/redis/RedisMiniServer.java b/redis/src/test/java/org/apache/calcite/adapter/redis/RedisMiniServer.java
index 018259c1888f..9e62fe6de9ad 100644
--- a/redis/src/test/java/org/apache/calcite/adapter/redis/RedisMiniServer.java
+++ b/redis/src/test/java/org/apache/calcite/adapter/redis/RedisMiniServer.java
@@ -70,18 +70,18 @@ private void makeData() {
       jedis.del("csv_03");
       jedis.del("csv_04");
       jedis.del("csv_05");
-      //set string
+      // set string
       jedis.set("raw_01", "123");
       jedis.set("json_01", "{\"DEPTNO\":10,\"NAME\":\"Sales\"}");
       jedis.set("csv_01", "10:Sales");
-      //set list
+      // set list
       jedis.lpush("raw_02", "book1");
       jedis.lpush("raw_02", "book2");
       jedis.lpush("json_02", "{\"DEPTNO\":10,\"NAME\":\"Sales1\"}");
       jedis.lpush("json_02", "{\"DEPTNO\":20,\"NAME\":\"Sales2\"}");
       jedis.lpush("csv_02", "10:Sales");
       jedis.lpush("csv_02", "20:Sales");
-      //set Set
+      // set Set
       jedis.sadd("raw_03", "user1");
       jedis.sadd("raw_03", "user2");
       jedis.sadd("json_03", "{\"DEPTNO\":10,\"NAME\":\"Sales1\"}");
@@ -95,7 +95,7 @@ private void makeData() {
       jedis.zadd("json_04", 2, "{\"DEPTNO\":11,\"NAME\":\"Sales2\"}");
       jedis.zadd("csv_04", 1, "10:Sales");
       jedis.zadd("csv_04", 2, "20:Sales");
-      //set map
+      // set map
       Map<String, String> raw5 = new HashMap<>();
       raw5.put("stuA", "a1");
       raw5.put("stuB", "b2");
diff --git a/site/_posts/2021-06-04-release-1.27.0.md b/site/_posts/2021-06-04-release-1.27.0.md
index 901c2b4abbf1..3442823545e1 100644
--- a/site/_posts/2021-06-04-release-1.27.0.md
+++ b/site/_posts/2021-06-04-release-1.27.0.md
@@ -33,7 +33,7 @@ is pleased to announce
 This release comes eight months after [1.26.0]({{ site.baseurl }}/docs/history.html#v1-26-0).
 It includes more than 150 resolved
 issues, comprising a few new features, three minor breaking changes, many bug-fixes and small
-improvements, as well as code quality enhancements and better test coverage. 
+improvements, as well as code quality enhancements and better test coverage.
 
 Among others, it is worth highlighting the following: