in core/src/main/java/org/apache/sling/cms/core/internal/operations/PropertyHintNodeNameGenerator.java [72:101]
public String filter(String nodeName) {
final StringBuilder sb = new StringBuilder();
char lastAdded = 0;
nodeName = nodeName.toLowerCase();
for (int i = 0; i < nodeName.length(); i++) {
final char c = nodeName.charAt(i);
char toAdd = c;
if (allowedChars.indexOf(c) < 0) {
if (lastAdded == replacementChar) {
// do not add several _ in a row
continue;
}
toAdd = replacementChar;
} else if (i == 0 && Character.isDigit(c)) {
sb.append(replacementChar);
}
sb.append(toAdd);
lastAdded = toAdd;
}
if (sb.length() == 0) {
sb.append(replacementChar);
}
return sb.toString();
}