| Flags `instanceof` checks where the expression can be determined to be a | |
| supertype of the type it is compared to. | |
| [JLS 15.28](https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.28) | |
| specifically calls `instanceof` out as *not* being a compile-time constant | |
| expression, so the usage of this pattern can lead to unreachable code that won't | |
| be flagged by the compiler: | |
| ```java | |
| class Foo { | |
| void doSomething() { | |
| if (this instanceof Foo) { // BAD: always true | |
| return; | |
| } | |
| interestingProcessing(); | |
| } | |
| } | |
| ``` | |
| In general, an `instanceof` comparison against a superclass is equivalent to a | |
| null check: | |
| ```java | |
| foo instanceof Foo | |
| ``` | |
| ```java | |
| foo != null | |
| ``` |