Error Updating Record Flag

[Daniel Simpson]

In my delete method, I need to change the flag from 00 to 0xFF. I do this:

dbReader.writeByte(0xFF);

However, when I do tests, I get strange results because of that value I know that when I read 0xFF from my datafile, it comes out as -1. Am I using the correct write method to write 0xFF. Does the negative sign count as a byte? Because that may be why my program is getting thrown off? I ran a simple test where I updated the flag in my first record by executing the code above. When I then ran my class to read all my records, I get weird results. However, when I went back and executed the line above, but instead wrote dbReader.writeByte(00), and ran my class again, it worked perfectly. So something is getting messed up when I write 0xFF. Any ideas on why it is doing this?

Here's a snippet of my code just so you can understand what's going on:

//creates an ArrayList to hold Contractor objects
        records = new ArrayList();
        // sets file pointer to the end of the schema
        dbReader.seek(schemaLength);
        int x = 0;
        // it will read all of the records until the end of the file
        //while(dbReader.getFilePointer() < dbReader.length()) {
            while(x < 2) {
            // creates array to hold 6 data field values
            String[] recordValues = new String[6];
            // reads value of flag in record
            byte flag = dbReader.readByte();
            System.out.println(flag);
            
            //if record is valid
            if(flag == 0) {             
                for(int i = 0; i < numberOfRecordFields; i++) { 
                    // holds the length of datafield in a byte array
                    byte[] dataField = new byte[fieldLengths[i]];
                    dbReader.readFully(dataField);
                    // converts byte data to textual String
                    String stringData = new String(dataField, "US-ASCII");      
                    recordValues[i] = stringData;
                }
                // adds new Contractor object to ArrayList
                records.add(new Contractor(recordValues, recordNumber));
            }
            else if(flag == -1) { // the flag indicates that the record is deleted
                // adds new Contractor object to ArrayList with null as
                // recordValues indicating that this is a deleted record
                records.add(new Contractor(recordValues, recordNumber));                
            }
            else {
                System.out.println("CRAP!");
            }  

I just wanted to read 2 records and see what the results were. My first record's flag is -1 (0xFF) and the 2nd record's flag is 0. Here is what I get when I do my output:

-1
66
CRAP!

[ November 21, 2004: Message edited by: Daniel Simpson ]

[Matt Sheehan.]

However, when I do tests, I get strange results because of that value I know that when I read 0xFF from my datafile, it comes out as -1.

Since a byte is a signed number in Java, its interpreted as -1, so thats the correct result.

As for your code, it may be that you need to insert

dbReader.skipBytes(totalRecordLength);

into your flag == -1 clause.
[ November 21, 2004: Message edited by: Matt Sheehan. ]

[Daniel Simpson]

I figured out what happend thanks to you!!!

    
            //if record is valid
            if(flag == 0) {             
                for(int i = 0; i < numberOfRecordFields; i++) { 
                    // holds the length of datafield in a byte array
                    byte[] dataField = new byte[fieldLengths[i]];
                    dbReader.readFully(dataField);
                    // converts byte data to textual String
                    String stringData = new String(dataField, "US-ASCII");      
                    recordValues[i] = stringData;
                }
                // adds new Contractor object to ArrayList
                records.add(new Contractor(recordValues, recordNumber));
            }
            else if(flag == -1) { // the flag indicates that the record is deleted
                // adds new Contractor object to ArrayList with null as
                // recordValues indicating that this is a deleted record
                records.add(new Contractor(recordValues, recordNumber));                
            }

What happens is, is that if the flag is -1, all it will do will insert null values into my contractor object. HOWEVER, it doesn't skip the bytes, so the next time I tried to read the second record, it attempts to read the flag from my first datafield. Thank you!!!
[ November 21, 2004: Message edited by: Daniel Simpson ]

[Anton Golovin]

Try raf.writeByte((byte)0xFF);