How to add single item to arraylist for multiple time with out using for loop

Question

In my application contains one Arraylist which i am adding value for every minute.

Initially I want to add one value for thousands time for that arraylist for that my code is

int count = 30000; Arraylist mylist = new Arraylist();for(int i=0;i<count;i++)
{
    mylist.add("4.5");
}

In the above code it is taking large time to complete the for loop and my app is getting slow . Is there any alternate way to add the value to array list fastly with one click?

score 6 · Accepted Answer · answered Nov 02 '17 at 06:48

6

You can use Collections's static <T> List<T> nCopies(int n, T o):

List<String> list = Collections.nCopies("4.5",count);

However, that would create an immutable List<String>. In order to obtain a mutable List, you'll have to pass that list to ArrayList's constructor, so I'm not sure the end result will be much faster than your current loop.

List<String> mylist = new Arraylist<>(Collections.nCopies("4.5",count));

answered Nov 02 '17 at 06:48

Eran

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Thanks for u r reply...one more small doubt how to add values from index 2 – VenkataKishore A Nov 02 '17 at 07:22
@VenkataKishoreA What do you mean? Do you want index 0 and index 1 to remain 0? You can set them to 0 after initializing the ArrayList. – Eran Nov 02 '17 at 07:23
yes i am adding mylist.add(5.0),mylist.add(1.0); and myList = new ArrayList(Collections.nCopies(secondsinfo, 4.5));but arraylist is starting from 4.5 – VenkataKishore A Nov 02 '17 at 07:28
@VenkataKishoreA Add `mylist.set(0,0.0);mylist.set(1,0.0);` – Eran Nov 02 '17 at 07:29

How to add single item to arraylist for multiple time with out using for loop

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