+ protected static boolean isSubstringOfDigits(String value, int offset, int length) {
+ if (value == null) {
+ return false;
+ }
+ int stringLength = value.length();
+ int max = offset + length;
+ if (stringLength < max) {
+ return false;
+ }
+ for (int i = offset; i < max; i++) {
+ char c = value.charAt(i);
+ if (c < '0' || c > '9') {
+ return false;
+ }
+ }
+ return true;
+ }
+