Converting EBCDIC to ASCII in java

If I am interpreting this format correctly you have a binary file format with fixed-length records. Some of these records are not character data (COBOL computational fields?)

So, you will have to read the records using a more low-level approach processing individual fields of each record:

import java.io.*;

public class Record {
  private byte[] kdgex = new byte[2]; // COMP
  private byte[] b1code = new byte[2]; // COMP
  private byte[] b1number = new byte[8]; // DISPLAY
  // other fields

  public void read(DataInput data) throws IOException {
    data.readFully(kdgex);
    data.readFully(b1code);
    data.readFully(b1number);
    // other fields
  }

  public void write(DataOutput out) throws IOException {
    out.write(kdgex);
    out.write(b1code);
    out.write(b1number);
    // other fields
  }
}

Here I've used byte arrays for the first three fields of the record but you could use other more suitable types where appropriate (like a short for the first field with readShort.) Note: my interpretation of the field widths is likely wrong; it is just an example.

The DataInputStream is generally used as a DataInput implementation.

Since all characters in the source and target encodings use a one-octet-per code point you should be able to transcode the character data fields using a method like this:

public static byte[] transcodeField(byte[] source, Charset from, Charset to) {
  byte[] result = new String(source, from).getBytes(to);
  if (result.length != source.length) {
    throw new AssertionError(result.length + "!=" + source.length);
  }
  return result;
}

I suggest tagging your question with COBOL (assuming that is the source of this format) so that someone else can speak with more authority on the format of the data source.

I also faced same issue like converting EBCDIC to ASCII string. Please find the code below to convert a single EBCDIC to ASCII string.

public class EbcdicConverter
{
    public static void main(String[] args) 
        throws Exception
    {
        String ebcdicString =<your EBCDIC string>;
        // convert String into InputStream
        InputStream is = new ByteArrayInputStream(ebcdicString.getBytes());
        ByteArrayOutputStream baos=new ByteArrayOutputStream();

        int line;
         while((line = is.read()) != -1) {
             baos.write((char)line);
         }
         String str = baos.toString("Cp500");
         System.out.println(str);
    }
}