How to convert a comma separated String to ArrayList in Java

Question

I have a comma separated String which i need to convert to ArrayList . I tried this way

import java.util.ArrayList;
import java.util.Arrays;

    public class Test {

        public static void main(String[] args) {

            String CommaSeparated = "item1 , item2 , item3";

            ArrayList<String> items = (ArrayList)Arrays.asList(CommaSeparated.split("\\s*,\\s*"));

            for(String str : items)
            {
                System.out.println(str);
            }

        }

    }

Its giving me the Runtime Error as shown

Exception in thread "main" java.lang.ClassCastException: java.util.Arrays$ArrayList cannot be cast to java.util.ArrayList
    at com.tradeking.at.process.streamer.Test.main(Test.java:14)

as i was trying to convert an List to arrayList by force .

try `ArrayList items = new ArrayList(Arrays.asList(CommaSeparated.split("\\s*,\\s*")))` — user902383, Aug 07 '13 at 13:12
This question may be of use: http://stackoverflow.com/questions/4658867/why-does-arrays-aslist-return-its-own-arraylist-implementation — Adil, Aug 07 '13 at 13:16

Rohit Jain · Accepted Answer · 2015-11-16T06:19:51.437

19

The ArrayList returned by Arrays.asList is not java.util.ArrayList. It's java.util.Arrays.ArrayList. So you can't cast it to java.util.ArrayList.

You need to pass the list to the constructor of java.util.ArrayList class:

List<String> items = new ArrayList<String>(Arrays.asList(CommaSeparated.split("\\s*,\\s*")));

or, you can simply assign the result:

List<String> items = Arrays.asList(CommaSeparated.split("\\s*,\\s*"));

but mind you, Arrays.asList returns a fixed size list. You cannot add or remove anything into it. If you want to add or remove something, you should use the 1st version.

P.S: You should use List as reference type instead of ArrayList.

edited Nov 16 '15 at 06:19

answered Aug 07 '13 at 13:12

Rohit Jain

209,639
45
409
525

It's super annoying that they used the same name `ArrayList` twice :) – arshajii Aug 07 '13 at 13:13
varargs do not help to split a string - above claim is wrong. – fjf2002 Nov 11 '15 at 17:26

score 2 · Answer 2 · answered Aug 07 '13 at 13:12

2

You can't just cast objects around like they're candy. Arrays.asList() doesn't return an ArrayList, so you can't cast it (it returns an unmodifiable List).

However you can do new ArrayList(Arrays.asList(...));

answered Aug 07 '13 at 13:12

Kayaman

72,141
5
83
121

It doesn't return an unmodifiable list, you can still call `set(...)` without any problems. – arshajii Aug 07 '13 at 13:19
@arshajii Fair enough, let's call it "constant sized list". – Kayaman Aug 07 '13 at 13:21

score 1 · Answer 3 · answered Aug 07 '13 at 13:13

1

Does it absolutely need to be an ArrayList? Typically you want to use the most generic form. If you're ok using a List just try:

List<String> items = Arrays.asList(...);

You can still iterate over it the same way you currently are.

answered Aug 07 '13 at 13:13

Chris Thompson

35,167
12
80
109

score 1 · Answer 4 · edited Aug 07 '13 at 13:40

1

String CommaSeparated = "item1 , item2 , item3";     
ArrayList<String> items = new ArrayList(Arrays.asList(CommaSeparated.split("\\s*,\\s*")));
for(String str : items)
{
    System.out.println(str);
}

edited Aug 07 '13 at 13:40

Will Eddins

13,628
5
51
85

answered Aug 07 '13 at 13:20

Kwak Young Ho

34
2

score 1 · Answer 5 · answered Aug 07 '13 at 13:20

Please try to use bellow code.

String[] temp;

    /* delimiter */
    String delimiter = ",";
    /*
     * given string will be split by the argument delimiter provided.
     */
    temp = parameter.split(delimiter);
    ArrayList<String> list = new ArrayList<String>();

    for (int l = 0; l < temp.length; l++)

    {

        list.add(temp[l]);

    }

How to convert a comma separated String to ArrayList in Java

5 Answers5