Created attachment 27567 [details]
Patch.

I need to detect whether a given HSSFSheet already has DataValidation settings applied.
The DataValidityTable class already has a visitContainedRecords(RecordVisitor) method, that is currently inaccessible from both HSSFSheet and user code.

The following patch suggests to add a method 

public void visitValidationData(RecordVisitor rv)

to HSSFSheet to iterate through the DataValidation records.
Use it like this:

final RecordVisitor rv = new RecordVisitor() {
  @Override
  public void visitRecord(Record r) {
    if (r instanceof DVRecord){
      final DVRecord dr = (DVRecord) r;
      // So there's the validation
      if (dr.getDataType() == ValidationType.LIST){
           // There is a DROP DOWN list! Use dr.* to examine location and content.
      }
    }
  }
};
sheet.visitValidationData(rv);



The XSSFSheet already provides a getDataValidations() method,