DeprecatedInputFormatWrapper.java

    @Override
    public boolean next(K key, V value) throws IOException {
      if (eof) {
        return false;
      }

      if (firstRecord) { // key & value are already read.
        firstRecord = false;
        return true;
      }

      try {
        if (realReader.nextKeyValue()) {

					if (key != realReader.getCurrentKey()) {

            throw new IOException("DeprecatedInputFormatWrapper can not "
                + "support RecordReaders that don't return same key & value "
                + "objects. current reader class : " + realReader.getClass());
					}

					if (value != realReader.getCurrentValue()) {
						if (null != valueCopier)
							valueCopier.copyValue(value, realReader.getCurrentValue());
						else {
							throw new IOException("DeprecatedInputFormatWrapper - value is different "
									+ "and no value copier provided. "
									+ "current reader class : " + realReader.getClass());
          }
					}
          return true;
        }
      } catch (InterruptedException e) {
        throw new IOException(e);
      }

      eof = true; // strictly not required, just for consistency
      return false;
    }