diff --git a/kernel/kernel-defaults/src/main/java/io/delta/kernel/defaults/internal/expressions/SubstringEvaluator.java b/kernel/kernel-defaults/src/main/java/io/delta/kernel/defaults/internal/expressions/SubstringEvaluator.java
index 2830e5012c4..5537ab4afae 100644
--- a/kernel/kernel-defaults/src/main/java/io/delta/kernel/defaults/internal/expressions/SubstringEvaluator.java
+++ b/kernel/kernel-defaults/src/main/java/io/delta/kernel/defaults/internal/expressions/SubstringEvaluator.java
@@ -106,7 +106,7 @@ public String getString(int rowId) {
         String inputString = input.getString(rowId);
         int position = positionVector.getInt(rowId);
         Optional<Integer> length = lengthVector.map(columnVector -> columnVector.getInt(rowId));
-        if (position > getStringLengthWithCodePoint(inputString)
+        if (position > getStringLength(inputString)
             || (length.isPresent() && length.get() < 1)) {
           return "";
         }
@@ -119,11 +119,11 @@ public String getString(int rowId) {
                   // e.g. Substring("aaa", -100, 95), should be read as Substring("aaa", 0, 0)
                   int endIndex =
                       Math.min(
-                          getStringLengthWithCodePoint(inputString),
+                          getStringLength(inputString),
                           Math.max(startPosition + len, 0));
-                  return subStringWithCodePoint(inputString, startIndex, Optional.of(endIndex));
+                  return getSubstring(inputString, startIndex, Optional.of(endIndex));
                 })
-            .orElse(subStringWithCodePoint(inputString, startIndex, Optional.empty()));
+            .orElse(getSubstring(inputString, startIndex, Optional.empty()));
       }
     };
   }
@@ -140,18 +140,19 @@ public String getString(int rowId) {
   private static int buildStartPosition(String inputString, int pos) {
     // Handles the negative position (substring("abc", -2, 1), the start position should be 1("b"))
     if (pos < 0) {
-      return getStringLengthWithCodePoint(inputString) + pos;
+      return getStringLength(inputString) + pos;
     }
     // Pos is 1 based and pos = 0 is treated as 1.
     return Math.max(pos - 1, 0);
   }
 
   /** Returns code point based string length for handling surrogate pairs. */
-  private static int getStringLengthWithCodePoint(String s) {
+  private static int getStringLength(String s) {
     return s.codePointCount(/* beginIndex = */ 0, s.length());
   }
 
-  private static String subStringWithCodePoint(String s, int start, Optional<Integer> end) {
+  /** Returns code point based substring for handling surrogate pairs. */
+  private static String getSubstring(String s, int start, Optional<Integer> end) {
     int startIndex = s.offsetByCodePoints(/* beginIndex = */ 0, start);
     return end.map(e -> s.substring(startIndex, s.offsetByCodePoints(0, e)))
         .orElse(s.substring(startIndex));