| 场景 | 到处判 null/缺省值、默认行为重复 |
|---|---|
| 形态 | Null Object、Unknown Customer |
| 收益 | 调用方不再遍地形如 if (x == null) |
Java 示例
Java 示例
class UnknownCustomer implements Customer {
public String name() { return "occupant"; }
public BillingPlan plan() { return BillingPlan.basic(); }
}