OverrideRecordReader.java 文件源码

@SuppressWarnings("unchecked") // Explicit check for value class agreement
public V createValue() {
  if (null == valueclass) {
    Class<?> cls = kids[kids.length -1].createValue().getClass();
    for (int i = kids.length -1; cls.equals(NullWritable.class); i--) {
      cls = kids[i].createValue().getClass();
    }
    valueclass = cls.asSubclass(Writable.class);
  }
  if (valueclass.equals(NullWritable.class)) {
    return (V) NullWritable.get();
  }
  return (V) ReflectionUtils.newInstance(valueclass, null);
}