迪米特法则(LOD)

1.高内聚:把相似功能放在同一类中，方便集中修改，类似单一职责

2.低耦合:类与类之间尽量减少依赖，关系尽量简单

迪米特法则：不该有直接依赖的类之间，不要有依赖，有依赖关系的类之间，尽量只依赖必要的接口

Each unit should have only limited knowledge about other units:only units '' closely '' related to the current unit.

Or : Each unit should only talk to its friends; Don't talk strangers.