filter input stream class

例句：

1. 1. The coffee is so strong thatit needs to be filtered before drinking.
   咖啡太浓了，需要过滤后才能喝。
2. 2. The scientist used a filter to removeimpurities from the water.
   科学家用过滤器从水中去除杂质。
3. 3. Thefilter in the machine canhelp to clean the air beforeit reaches the room.
   机器中的过滤器可以帮助净化空气，使其在到达房间之前保持清洁。