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I know that the () in ArrayList<Integer> = new ArrayList<>() can be used to describe the capacity for the ArrayList, but recently I've seen people put ArrayLists in the () of other ArrayLists.
I wasn't able to find the answer from searching on Google multiple times, any ideas?
This is a call to the ArrayList(Collection<T>) constructor. It creates a new array list with the elements of the Collection (e.g., another ArrayList) being passed to the constructor.
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object Test extends App {
val i: Iterable[(String, Long)] = List(("a", 1), ("b", 2))
val sortedMap: SortedMap[String, Long] = i.toList.sortBy(_._2)
}
I don't want to convert Iterable to List/Array etc since it's coming form a jdbc query.
You can't do that. SortedMap sorts by keys, not values.
If you want it sorted by value, you gotta use ListMap, and can't avoid converting to List:
ListMap(i.toList.sortBy(-_._2):_*)
There isn't really too much wrong with converting to list, since you are loading the whole thing in memory anyway. This is faster too, than building a tree one element at a time.
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If I have an initialized array in Java and I want to do a method to one element in that array I would do
array[n].method();
but how do I do the same thing with an arraylist?
arraylist[n].method() gives me an error.
With Java use get method with ArrayList:
arraylist.get(n).method();
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Is it possible to search without iterator without using map.
Map<String,Short> map = new HashMap<String,Short>();
map.put("String2", (short)2);
map.put("String1", (short)1);
map.put("String3", (short)4);
I am looking for a way to get the value based on the key (Return 2 for value String2). Is Map the right one to use in this scenario.
Thanks !
Returning values based on a key is precisely what maps are for.
To retrieve your value you can simply do:
short returnVal = map.get("String2");
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I have a List<A> of data, and wanna store it to the other list(List<B>).
any suggestion to make it possible?
You can use the Collections.copy(ListA, ListB) method, or even, if you're working with ArrayLists: ListB = ListA.clone()
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I've got many resources with names based on a pattern:
R.drawable.small_house_red
R.drawable.small_house_blue
R.drawable.big_house_black
R.drawable.small_tree_red
I've got 3 strings: size, type, color. I can put all required resources to map, and get them by concated string but is it possible to get them without manually entering all combinations to the map?
You can use this
int id = context.getResources().getIdentifier("imageNameAsString", "drawable", context.getPackageName());