String set to ArrayList?

Question

So I was looking up how to change a String set to an ArrayList<sSring> and I couldn't find anything. I tried:

favorites  = new ArrayList( mPrefsaved.getStringSet("faves", null) ;

How can I convert a StringSet into an ArrayList<string>?

I tried:

  private void getsaved() {

      favorites = new ArrayList<String>(mPrefsaved.getStringSet("faves", null));

}

But log Cat told me NullPointerException

What is a String Set? – Sotirios Delimanolis Dec 26 '13 at 15:22 — Sotirios Delimanolis, Dec 26 '13 at 15:22
A closing paranthesis would help to begin with. – Keppil Dec 26 '13 at 15:25 — Keppil, Dec 26 '13 at 15:25
Is StringSet your own object? – Mike M Dec 26 '13 at 15:27 — Mike M, Dec 26 '13 at 15:27

score 12 · Answer 1 · answered Dec 26 '13 at 15:25

12

Consider you have a set of Strings like

Set<String>  set = new HashSet<String>();
 // some elements in set

then you can try

 List<String>  listFromSet = new ArrayList<String>(yourCurrentSet);

in your case .

 List<String>  listFromSet = new ArrayList<String>(mPrefsaved.getStringSet("faves", null));

Make sure that your method getStringSet returns a collection of Strings.

answered Dec 26 '13 at 15:25

Suresh Atta

it returns an error of Null Pointer Exception using the method on the bottom. I know that myPrefsaved returns a set value because I use it in another activity where it retrieves the data into a string set – JavaGrassHopper Dec 26 '13 at 15:50
Have you initialized `mPrefsaved` ? is it null ? – Suresh Atta Dec 26 '13 at 16:18
mPrefsaved =getSharedPreferences("MyPreferences", 0); yes – JavaGrassHopper Dec 26 '13 at 20:48

score 6 · Accepted Answer · answered Dec 26 '13 at 15:27

6

Use foreach in stringset and add each string to arraylist

ArrayList<String> arrayList = new ArrayList<String>();
for (String str : stringset)  
    arrayList.add(str);

answered Dec 26 '13 at 15:27

henry4343

I got a null pointer exception – JavaGrassHopper Dec 26 '13 at 15:56
@user3127974 Can you please post the stacktrace ? – Suresh Atta Dec 26 '13 at 16:56
@sᴜʀᴇsʜᴀᴛᴛᴀ whats that ? – JavaGrassHopper Dec 26 '13 at 20:56
@user3127974 Stack trace in the sense :http://stackoverflow.com/questions/3988788/what-is-a-stack-trace-and-how-can-i-use-it-to-debug-my-application-errors – Suresh Atta Dec 27 '13 at 04:35
3

The Simplest way is ArrayList arrayList = new ArrayList<>(StringSet) – Jeffrey Aug 15 '18 at 18:39

2 Answers2