public ReturnCode filterColumn(Cell cell) {
    int qualifierLength = cell.getQualifierLength();
    if (qualifierLength < prefix.length) {
      int cmp = compareQualifierPart(cell, qualifierLength, this.prefix);
      if (cmp <= 0) {
        return ReturnCode.SEEK_NEXT_USING_HINT;
      } else {
        return ReturnCode.NEXT_ROW;
      }
    } else {
      int cmp = compareQualifierPart(cell, this.prefix.length, this.prefix);
      if (cmp < 0) {
        return ReturnCode.SEEK_NEXT_USING_HINT;
      } else if (cmp > 0) {
        return ReturnCode.NEXT_ROW;
      } else {
        return ReturnCode.INCLUDE;
      }
    }
  }
This filter is used for selecting only those keys with columns that matches a particular prefix.
For example, if prefix is 'an', it will pass keys with columns like 'and', 'anti' but not keys
with columns like 'ball', 'act'.
hbase-client/src/main/java/org/apache/hadoop/hbase/filter/ColumnPrefixFilter.java