private void constrain() {
   BigInteger offset = new BigInteger(Integer.toString(addressSize * (numUsableRows)));
   BigInteger endVal = startVal.add(offset);
   if (endVal.compareTo(scrollBar.getMaximumHP()) > 0) {
     startVal = scrollBar.getMaximumHP().subtract(offset);
     endVal = scrollBar.getMaximumHP();
     scrollBar.setValueHP(startVal);
     model.fireTableDataChanged();
   }
 }
 private void updateFromScrollBar() {
   beginUpdate();
   BigInteger oldStartVal = startVal;
   startVal = scrollBar.getValueHP();
   constrain();
   model.fireTableDataChanged();
   if (oldStartVal != null) {
     modifySelection(oldStartVal.subtract(startVal).intValue() / addressSize);
   }
   endUpdate();
 }
 private String bigIntToHexString(BigInteger bi) {
   StringBuffer buf = new StringBuffer();
   buf.append("0x");
   String val = bi.toString(16);
   for (int i = 0; i < ((2 * addressSize) - val.length()); i++) {
     buf.append('0');
   }
   buf.append(val);
   return buf.toString();
 }