Use static method
diff --git a/src/main/java/org/apache/commons/text/numbers/DoubleFormat.java b/src/main/java/org/apache/commons/text/numbers/DoubleFormat.java
index ec7319d..407ba68 100644
--- a/src/main/java/org/apache/commons/text/numbers/DoubleFormat.java
+++ b/src/main/java/org/apache/commons/text/numbers/DoubleFormat.java
@@ -499,7 +499,7 @@
* @param symbols symbols object
* @return string containing the localized digits 0-9
*/
- private String getDigitString(final DecimalFormatSymbols symbols) {
+ private static String getDigitString(final DecimalFormatSymbols symbols) {
final int zeroDelta = symbols.getZeroDigit() - DEFAULT_DECIMAL_DIGITS.charAt(0);
final char[] digitChars = new char[DEFAULT_DECIMAL_DIGITS.length()];