fix syntax 21 code

Signed-off-by: xinyual <xinyual@amazon.com>

Author: xinyual

core/src/main/java/org/opensearch/sql/calcite/CalciteRexNodeVisitor.java

@@ -16,16 +16,13 @@
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
-<<<<<<< HEAD
 import java.util.stream.Collectors;
 
-=======
 import java.util.Locale;
 import java.util.Map;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import javax.annotation.Nullable;
->>>>>>> 122ae79ad (Add lambda function and array related functions (#3584))
 import lombok.RequiredArgsConstructor;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.type.RelDataType;
@@ -395,7 +392,7 @@ public CalcitePlanContext prepareLambdaContext(
       candidateType.add(
           ((ArraySqlType) previousArgument.get(0).getType())
               .getComponentType()); // The first argument should be array type
-      candidateType.addAll(previousArgument.stream().skip(1).map(RexNode::getType).toList());
+      candidateType.addAll(previousArgument.stream().skip(1).map(RexNode::getType).collect(Collectors.toList()));
       candidateType =
           modifyLambdaTypeByFunction(functionName, candidateType, defaultTypeForReduceAcc);
       List<QualifiedName> argNames = node.getFuncArgs();

core/src/main/java/org/opensearch/sql/expression/function/CollectionUDF/ArrayFunctionImpl.java

@@ -113,7 +113,8 @@ public static Object internalCast(Object... args) {
                 .map(i -> (Object) ((Number) i).floatValue())
                 .collect(Collectors.toList());
         break;
-      case VARCHAR, CHAR:
+      case VARCHAR:
+      case CHAR:
         result = originalList.stream().map(i -> (Object) i.toString()).collect(Collectors.toList());
         break;
       default:

core/src/main/java/org/opensearch/sql/expression/function/CollectionUDF/LambdaUtils.java

@@ -45,7 +45,8 @@ public static RelDataType inferReturnTypeFromLambda(
     List<RexNode> lambdaOperands = rexCall.getOperands();
     List<RexNode> filledOperands = new ArrayList<>();
     for (RexNode rexNode : lambdaOperands) {
-      if (rexNode instanceof RexLambdaRef rexLambdaRef) {
+      if (rexNode instanceof RexLambdaRef) {
+        RexLambdaRef rexLambdaRef = (RexLambdaRef) rexNode;
         if (rexLambdaRef.getType().getSqlTypeName() == SqlTypeName.ANY) {
           filledOperands.add(
               new RexLambdaRef(
@@ -71,7 +72,8 @@ public static RexCall reInferReturnTypeForRexCallInsideLambda(
     List<RexNode> filledOperands = new ArrayList<>();
     List<RexNode> rexCallOperands = rexCall.getOperands();
     for (RexNode rexNode : rexCallOperands) {
-      if (rexNode instanceof RexLambdaRef rexLambdaRef) {
+      if (rexNode instanceof RexLambdaRef) {
+        RexLambdaRef rexLambdaRef = (RexLambdaRef) rexNode;
         filledOperands.add(
             new RexLambdaRef(
                 rexLambdaRef.getIndex(),