Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/5124#discussion_r27306885
--- Diff: core/src/main/scala/org/apache/spark/SparkContext.scala ---
@@ -474,13 +477,13 @@ class SparkContext(config: SparkConf) extends Logging
with ExecutorAllocationCli
* Spark fair scheduler pool.
*/
def setLocalProperty(key: String, value: String) {
- if (localProperties.get() == null) {
- localProperties.set(new Properties())
+ if (localProperties.get().isEmpty) {
+ localProperties.set(Some(new Properties()))
--- End diff --
Option helps you avoid NPEs by convention; it's not guaranteed to _prevent_
NPE, since you can still do things like this:
```scala
scala> var x: Option[Int] = null
x: Option[Int] = null
scala> x
res0: Option[Int] = null
scala> x.get
java.lang.NullPointerException
... 33 elided
scala> x match { case Some(_) => (); case None => () }
scala.MatchError: null
... 33 elided
```
There's actually a small risk of this issue occurring when you're not
methodical when refactoring existing null-passing code to pass options. If you
have something like `def foo(x: String)` and you refactor it to `def foo(x:
Option[String])`, you'll still run into trouble if you had old code that called
`foo(null)`, since this code will still compile correctly after the
refactoring. This means that you have to search for all callers of `foo()`
when performing the refactoring, rather than just changing the type and fixing
whatever compiler errors occur. A similar problem can occur if you call
`Some(x)` where `x == null`, which can also happen when refactoring large
legacy codebases, since this causes you to wind up with a `Some(null)`.
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