1. 不可变的：而泛型是不可变的(invariant),List不会是List_{的基类,更不会是它的子类. 数组的协变性可能会导致一些错误,比如下面的代码:}

2. 不变性：Evans DDD在领域对象的生命周期中对不变性(invariant)进行了定义,指无论何时数据发生变化,都必须满足所有对象一致变化的规则.

1. a feature (quantity or property or function) that remains unchanged when a particular transformation is applied to it

1. unvarying in nature

    e.g. maintained a constant temperature
           principles of unvarying validity

    Synonym: changelessconstantunvarying

2. unaffected by a designated operation or transformation