Converting 'ArrayList<String> to 'String[]' in Java

java arrays string arraylist collections
Alex picture Alex · Oct 28, 2010 · Viewed 720.1k times · Source

How might I convert an ArrayList<String> object to a String[] array in Java?

Answer

Bozho picture Bozho · Oct 28, 2010 
List<String> list = ..;
String[] array = list.toArray(new String[0]);

For example:

List<String> list = new ArrayList<String>();
//add some stuff
list.add("android");
list.add("apple");
String[] stringArray = list.toArray(new String[0]);

The toArray() method without passing any argument returns Object[]. So you have to pass an array as an argument, which will be filled with the data from the list, and returned. You can pass an empty array as well, but you can also pass an array with the desired size.

Important update: Originally the code above used new String[list.size()]. However, this blogpost reveals that due to JVM optimizations, using new String[0] is better now.

Related questions

Print a string from ArrayList of String[]?

I have an ArrayList full of strings arrays that I built like this: String[] words = new String[tokens.length]; I have three arrays like above in my ArrayList: surroundingWords.add(words); surroundingWords.add(words1); surroundingWords.add(words2); etc Now if …

Read More
How to add new elements to an array?

I have the following code: String[] where; where.append(ContactsContract.Contacts.HAS_PHONE_NUMBER + "=1"); where.append(ContactsContract.Contacts.IN_VISIBLE_GROUP + "=1"); Those two appends are not compiling. How would that work correctly?

Read More
How to convert Java String into byte[]?

Is there any way to convert Java String to a byte[] (not the boxed Byte[])? In trying this: System.out.println(response.split("\r\n\r\n")[1]); System.out.println("******"); System.out.println(response.split("\r\n\r\n")[1].getBytes().…

Read More