Andrew's Read DB Method

[Shan Jun Hao]

Hi,

I am trying to do what Andrew has demostrated in his book.

class RecordFieldReader {
    private int readerOffset = 0;
            
    String read(int length) throws UnsupportedEncodingException {
        String str = new String(input, readerOffset, length, "UTF-8");
        
    readerOffset += length;
    return str.trim();
}
 
RecordFieldReader readRecord = new RecordFieldReader();
 
short DELETED_FLAG = Short.valueOf(readRecord.read(2)).shortValue();
 
//read the rest of the fields... blah blah blah

I keep on getting errors with the short value - java.lang.NumberFormatException: For input string: "". Can anyone tell me how to convert the String to a short value?

[Petr Hejl]

You read two bytes, that I believe creates String with characters below ' ' (0x32). So it is trimmed to "" (as described in api for trim).

[Daniel Bryant]

Shan,

I personally read the two bytes indicating a deleted flag before reading the rest of the record from the file - that way you can read the two bytes directly into a byte array (bypassing the need for conversion) and check if the record is deleted or not.

The added bonus of this approach is that if you determine a record is deleted you do not need to read the rest of the record, and accordingly save valuable time synchronizing and reading the DB file.

Best wishes,

Daniel