how could I set my object to another in lambda expression? I got error
variable used in lambda expression should be final or effectively final
with following code:
public MyObj myFun(MyObj o) {
MyObj obj = null;
myObjList.stream().filter(o -> ...).forEach(o -> {
// I do some stuff here
// I need here set obj to o, but I got error
obj = o;
});
return myObj; // I need return found obj or null;
}
You can't assign o to the outer variable. But you can return it as a result of you stream processing. Use map instead of forEach and return o from the mapper. Then do findAny or findFirst - this will give you an Optional<MyObj>. Finally do orElse(null) to return the found and processed object or null if none was found.
MyObj obj = myObjList
.stream()
.filter(o -> ...)
.map(o -> {
// I do some stuff here
// I need here set obj to o, but I got error
return o;
})
.findAny()
.orElse(null);
Instead of using forEach instead consider using map(o->{...}).findFirst().get() (or similar depending on your logic if no item is relevant - your null case).
In general, you should let streams finish in a collector or a selector (findFirst/findAny etc.) because that will allow you to write simpler and clearer code
Instead of streaming through it, you could simply iterate through it in a loop and then return the value when you find it.
The streamy sort of answer is probably to use something like findFirst.
