ex00 commented on a change in pull request #8632: [FLINK-12744][ml] add shared
params in ml package
URL: https://github.com/apache/flink/pull/8632#discussion_r293098782
##########
File path:
flink-ml-parent/flink-ml-api/src/main/java/org/apache/flink/ml/api/misc/param/Params.java
##########
@@ -47,14 +70,33 @@
* @throws RuntimeException if the Params doesn't contains the specific
parameter, while the
* param is not optional but has no default
value in the {@code info}
*/
- @SuppressWarnings("unchecked")
public <V> V get(ParamInfo<V> info) {
- V value = (V) paramMap.getOrDefault(info.getName(),
info.getDefaultValue());
- if (value == null && !info.isOptional() &&
!info.hasDefaultValue()) {
- throw new RuntimeException(info.getName() +
- " not exist which is not optional and don't
have a default value");
+ Stream<V> stream = getParamNameAndAlias(info)
+ .filter(this.params::containsKey)
+ .map(x -> this.params.get(x))
+ .map(x -> valueFromJson(x, info.getValueClass()))
+ .limit(1);
Review comment:
> If not use stream object, we need more codes.
>
> For the value of parameter may be null, and the findFirst method is not
friendly for the null, thus we chose the limit(.) method.
>
> When the user sets a Null as the Value of Param, using the findFirst
method in the Stream class will throw NullPointerException.
> Looking deep into the code, findFirst returns an instance of Optional,
> but Optional can only use non-null value as a constructor argument.
> For example, the following code will throw NullPointerException.
> ` Stream.of(null, "2").findFirst(); `
I suppose if we will have `null` in the stream is an invalid state, and we
need to handle this situation.
anyway, we can filtering `null` before getting results, for e.g. by
`.filter(Objects::nonNull)`
I agree with @becketqin and @c4emmmm that the code without stream will be
much easier to reading
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