I have a stream, and I want to explicitly collect it into a HashMap. Right now, I'm doing something like
List<Item> listToTransform = //initialized and populated
HashMap<K, V> myHashMap = new HashMap<>();
listToTransform.stream().map(/* do my transformation here */)
.forEach(i -> myHashMap.put(i.getKey(), i.getValue()));
I was wondering if there was a way of using Collectors to explicitly get back a HashMap.
One of the overloads to the Collectors.toMap method will allow you to select a map implementation of your choice.
Unfortunately, one of the drawbacks to this overload is that it also requires a method to merge two values when they have the same key (though I often reference a method that always throws in that case).
HashMap<K, V> myHashMap = listToTransform.stream().map(/* do my transformation here */)
.collect(Item::getKey, Item::getValue, this::throwIllegalArgumentException, HashMap::new);
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