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I have the following the code currently.
Method - parseGreeting()
public GetGreetingNmsObjects parseGreeting(String greetingType, GetGreetingNmsResponse xmlFromNms) {
GetGreetingNmsObjects objectFound = null;
List<GetGreetingNmsObjects> objList = xmlFromNms.getObject();
for (GetGreetingNmsObjects obj : objList) {
List<Attribute> attrs = obj.getAttributes();
Optional<Boolean> found = attrs.stream()
.filter(a -> a.name.equals(GREETING_TYPE))
.map(a -> a.value.equals(greetingType))
.findAny();
if(found.get()) {
objectFound = obj;
break;
}
return objectFound;
}
GetGreetingNmsObjects .java
public class GetGreetingNmsObjects {
List<Attribute> attributeList;
public List<Attribute> getAttributes() {
return attributeList;
}
}
In the above method, is there a way to avoid the for loop and if statement and handle with streams itself?
I tried to use 'flatmap' and get the stream for 'attributesList' but once the match is found, I could not get reference to 'GetGreetingNmsObjects' object.
GetGreetingNmsObjects objectFound = objList.stream()
.flatMap(grt -> grt.getAttributes())
.filter(a -> a.name.equals(GREETING_TYPE))
.map(a -> a.value.equals(greetingType))
????
758
That means list. stream(). filter(i -> i >= 3); does not change original list. All stream operations are non-interfering (none of them modify the data source), as long as the parameters that you give to them are non-interfering too.
We can use a flatMap() method on a stream with the mapper function List::stream. On executing the stream terminal operation, each element of flatMap() provides a separate stream. In the final phase, the flatMap() method transforms all the streams into a new stream.
Does flatmap() method preserve the order of the streams? Yes, It does and map() also.
One approach is to use a terminal operation to collect the values of the stream to an ArrayList, and then simply use add(int index, E element) method. Keep in mind that this will give you the desired result but you will also lose the laziness of a Stream because you need to consume it before inserting a new element.
Your original code contains a logic error:
Optional<Boolean> found = …
.map(a -> a.value.equals(greetingType))
.findAny();
This will return the result of an arbitrary comparison, in a sequential context, it’s likely the result of the first element.
I’m quite sure that you actually want to know whether there is any matching element, hence, should use
boolean found = …
.anyMatch(a -> a.value.equals(greetingType));
This can be simply used as predicate to find the first element having the matching element:
return xmlFromNms.getObject().stream()
.filter(obj -> obj.getAttributes().stream()
.filter( a -> a.name.equals(GREETING_TYPE))
.anyMatch(a -> a.value.equals(greetingType)))
.findFirst().orElse(null);
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