Writable collections
- org.apache.hadoop.io包包含了6个Writable collection类型:
- ArrayWritable,TwoDArrayWritable是Writable实现了数组和二维数组的实例。所有的元素都必须是一个相同类的实例:
- ArrayWritable writable = new ArrayWritable(Text.class);
- ArrayPrimitiveWritable封装了Java的数组类型
- MapWritable实现了java.util.Map<Writable,Writable>
- SortedMapWritable实现java.util.SortedMap<WritableComparable,Writable>
- EnumSetWritable
- ArrayWritable,TwoDArrayWritable是Writable实现了数组和二维数组的实例。所有的元素都必须是一个相同类的实例:
- 对于一个单一类型的列表,ArrayWritable是足够的,但存储不同类型的Writable,可以使用GenericWritable也可以写一个ListWritable。