I am trying to declare an array of Set<String> so I do not have to manage each sets separately. But things go wrong:
ArrayList<Set<String>> categories=new LinkedHashSet<>();
Here, Java says that type Set<String> is erroneous and then reports an error.
If this is wrong, then how can I make an array of :
static Set<String> category1 = new LinkedHashSet<>();
You are initialising an ArrayList with LinkedHashSet object and hence the error:
ArrayList<Set<String>> categories=new LinkedHashSet<>();
change it to
ArrayList<Set<String>> categories=new ArrayList<>();
you need to use HashSet when you create a Set to be added into the list. Something like this:
Set<String> firstSet = new HashSet<String>();
//build your set
//add set to list
categories.add(firstSet);
Btw, you mentioned Array in your question description, so here is the declaraiton for plain array of Sets:
Set<String>[] categories=new HashSet[10];
Set<String>[] and ArrayList<Set<String>>?
You can do something like:
List<HashSet> list =new ArrayList<HashSet>();
HashSet<String> hs =new HashSet<String>();
hs.add(value1);
hs.add(value2);
list.add(hs);
You can use for or while loop to add values to set(hs) and then add the set to list.
LinkedHashSetis not anArrayListof anything.Sets individually. If that's a pain, make your own ListSet class and encapsulate the management.