CODEWITHSUNDEEP
javastringlistobjectset
chris123
chris123

Reputation: 197

Getting individual entries of a Set in Java?

So I am currently having a problem understanding how to access a set, is that even allowed? So I understand my set of names contains a set of Character objects. I also understand that my toString() method call converts these Character objects into a String, but not a conventional string -- which is why I have [s,a] rather than [sa]. So my question is, is if there is a way to make me have a list of individual strings. So I want my list to be = [s, a] rather than [ [s,a] ]. Is this even possible? I apologize if this makes no sense; nevertheless, if you do understand my fumbled explanation thank you for your time and help. If you need for me to explain more, I will. 

    //this all works
    Set<Character> names = find(prefix).getRollCall().keySet();
    //[s,a]
    String lists = names.toString();
    //[s,a]
    List<String> sloop = Arrays.asList(lists);
    //[[s,a]]

Upvotes: 0

Views: 56

Answers (3)

sprinter
sprinter

Reputation: 27946

Let me explain what's happening in your code, in case you aren't clear:

String lists = names.toString();

This calls the standard toString method for a collection which converts your set to an ordinary (conventional) string in a standard format (i.e. comma delimited, in brackets). There's nothing special about the string that is created: "[s, a]".

List<String> sloop = Arrays.asList(lists);

The asList method takes one or more arguments and converts them into a list. Because you've given it only a single argument lists it creates a list with a single string element: ("[s, a]")

Then, later, I suspect you are doing something like:

System.out.println(sloop);

This again calls the standard toString method for a collection (in this case the List sloop) and again creates a comma delimited, bracket enclosed standard string: "[[s, a]]"

So, most of that is probably not what you want. Your lists variable isn't a List, it's a String which I assume isn't what you want.

If you are just looking to convert your set of character to a list of strings, then this is pretty trivial in Java 8:

List<String> lists = names.stream().map(Character::toString).collect(Collectors.toList());

Upvotes: 1

user207421
user207421

Reputation: 310840

Don't use toString() at all. Iterate over the elements of the Set and build up whatever string you like.

Set<Character> names = find(prefix).getRollCall().keySet();
for (Character c : names)
{
    // whatever you like
}

Upvotes: 2

Paul Boddington
Paul Boddington

Reputation: 37645

If you want to convert a Set<Character> to a List<Character> you can do

List<Character> list = new ArrayList<Character>(set);

If you want to convert a Set<Character> to a List<String> you can do 

List<String> list = new ArrayList<String>();
for (char c : set)
    list.add("" + c);

Upvotes: 3

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