ArrayList initialized/accessed using Singleton class

Question

I am using an ArrayList in my application.

I would like to know the exact procedure to initialize my ArrayList from a Singleton class.
The data will be used in some other Activities.

Can anybody help to know about Singleton class?

Please, add some code and further explanation to help us understand the problem. — Mayuso, Oct 20 '16 at 11:31

HelloSadness · Accepted Answer · 2016-10-20T13:34:02.443

10

Here is how to create your singleton class :

    public class YourSingleton  {  

        private static YourSingleton mInstance;
        private ArrayList<String> list = null;

        public static YourSingleton getInstance() {
            if(mInstance == null)
                mInstance = new YourSingleton();

            return mInstance;
        }

        private YourSingleton() {
          list = new ArrayList<String>();
        }
        // retrieve array from anywhere
        public ArrayList<String> getArray() {
         return this.list;
        }
        //Add element to array
        public void addToArray(String value) {
         list.add(value);
        }
}

Anywhere you need to call your arrayList just do :

YourSingleton.getInstance().getArray();

To add elements to array use :

 YourSingleton.getInstance().addToArray("first value");

or

YourSingleton.getInstance().getArray().add("any value");

edited Oct 20 '16 at 13:34

answered Oct 20 '16 at 11:03

HelloSadness

945
7
17

Thanks @Anto.. and one more thing is can I use multiple arraylist in same singleton class – AndroidKing Oct 20 '16 at 11:07
yes you can, and create differents methods to call correct array. In this exemple you have getArray(). You could create getFirstArray(), getSecondArray() etc... Just add your others array in class declaration and initialize them in constructor just like i did for 'list' – HelloSadness Oct 20 '16 at 11:08
Got an Idea.. Very kind of you@Anto Lemme checkout and let u know – AndroidKing Oct 20 '16 at 11:10
How to set data in **list** from singleton class – AndroidKing Oct 20 '16 at 11:14
edited my post, you need to create a method that will affect the array – HelloSadness Oct 20 '16 at 11:16
Return statement missing know – AndroidKing Oct 20 '16 at 11:20
need a big help@Anto I have 3 ArrayLists, which are Name, Age, Location – AndroidKing Oct 20 '16 at 13:23
in those arraylist i would like to filter by all the three in searchview.. I mean if i wanna search using name or age or location.. how to filter this – AndroidKing Oct 20 '16 at 13:26
Then that is another question ;) create a new post with sample of your search code ! – HelloSadness Oct 20 '16 at 13:31
Sorry @Anto. What I need is Have to filter any one of the arraylist should filter all the three Values – AndroidKing Oct 20 '16 at 13:33
I cant add new question here:-( – AndroidKing Oct 20 '16 at 13:48

score 1 · Answer 2 · answered Oct 20 '16 at 10:58

1

Please look at the following wikipedia-artikle:

https://en.wikipedia.org/wiki/Singleton_pattern

But keep in mind that singletons are 'global state' and make your sourcecode harder to test. There are lot of people saying: "singletons are evil'

answered Oct 20 '16 at 10:58

Tobias Otto

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13
20

score 0 · Answer 3 · answered Oct 20 '16 at 11:01

I think you need something like this.

public class SingletonClass {

    private static ArrayList<String> strArray;
    private static SingletonClass singleton;

    private SingletonClass(){}

    public static synchronized SingletonClass getConnectionInstance(ArrayList<String> strArray){        
        if (singleton == null) {
             singleton = new SingletonClass();
        }
        this.strArray = strArray;
        return singleton;
    }
}

ArrayList initialized/accessed using Singleton class

3 Answers3

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