diff --git a/src/main/java/uk/ac/ebi/eva/evaseqcol/service/SeqColService.java b/src/main/java/uk/ac/ebi/eva/evaseqcol/service/SeqColService.java
index 3c81f27..3066beb 100644
--- a/src/main/java/uk/ac/ebi/eva/evaseqcol/service/SeqColService.java
+++ b/src/main/java/uk/ac/ebi/eva/evaseqcol/service/SeqColService.java
@@ -402,9 +402,9 @@ public String calculateSeqColLevelOneMapDigest(Map<String, String> seqColLevelOn
     private String convertSeqColLevelTwoAttributeValuesToString(List<?> seqColL2Attribute, SeqColExtendedDataEntity.AttributeType type) {
         switch (type) {
             case lengths: // List<Integer> type
-                return JSONIntegerListExtData.toString((List<Integer>) seqColL2Attribute);
+                return new JSONIntegerListExtData((List<Integer>) seqColL2Attribute).toString();
             default: // List<String> types
-                return JSONStringListExtData.toString((List<String>) seqColL2Attribute);
+                return new JSONStringListExtData((List<String>) seqColL2Attribute).toString();
         }
     }
 
diff --git a/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONIntegerListExtData.java b/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONIntegerListExtData.java
index 7c019b8..09abf2a 100644
--- a/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONIntegerListExtData.java
+++ b/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONIntegerListExtData.java
@@ -13,13 +13,6 @@ public JSONIntegerListExtData(List<Integer> object) {
         super(object);
     }
 
-    /**
-     * The same as the Overridden toString method
-     * // TODO: we can get rid of this method for List<Integer> types*/
-    public static String toString(List<Integer> object) {
-        return object.toString();
-    }
-
     @Override
     public String toString() {
         return this.object.toString();
diff --git a/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONStringListExtData.java b/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONStringListExtData.java
index 0b1e28d..4ec1066 100644
--- a/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONStringListExtData.java
+++ b/src/main/java/uk/ac/ebi/eva/evaseqcol/utils/JSONStringListExtData.java
@@ -13,29 +13,6 @@ public JSONStringListExtData(List<String> object) {
         super(object);
     }
 
-    /**
-     * The same as the Overridden toString method
-     * Used to avoid code duplication in different classes
-     * // TODO: We can find a better way to avoid code duplication*/
-    public static String toString(List<String> object) {
-        StringBuilder objectStr = new StringBuilder();
-        int arraySize = ((List<?>) object).size();
-        // Include quotes. Eg: ["aaa", "bbb", "ccc"].
-        objectStr.append("[");
-        for (int i=0; i<arraySize-1; i++) {
-            objectStr.append("\"");
-            objectStr.append(((List<?>) object).get(i));
-            objectStr.append("\"");
-            objectStr.append(",");
-        }
-        objectStr.append("\"");
-        objectStr.append(((List<?>) object).get(arraySize-1));
-        objectStr.append("\"");
-        objectStr.append("]");
-
-        return objectStr.toString();
-    }
-
     @Override
     public String toString() {
         StringBuilder objectStr = new StringBuilder();