Extract String[] elements from a list

Question

at my work I've got the following source code:

import java.util.ArrayList;
import java.util.List;

public class Temporaer
{
    public static void main(String[] args)
    {
        List stringArrayList = new java.util.ArrayList();
        stringArrayList.add(fillStringArrayElement("a", "b"));
        stringArrayList.add(fillStringArrayElement("c", "d"));

        String[] listElement;

        /*
         * I'm stuck here, because I don't know what I have to do
         */

        System.out.println(listElement.length);
    }

    //Just a method to fill a list easily
    private static String[] fillStringArrayElement (String firstElem, String secondElem)
    {
        String[] stringArrayListElement = new String[2];
        stringArrayListElement[0] = firstElem;
        stringArrayListElement[1] = secondElem;
        return stringArrayListElement;
    }
}

My goal is it to extract each list item and work with those.

I tried to use the toArray[T[]) method as mentioned here. Though it generates an java.lang.ArrayStoreException. Note: I cannot change the type of the list because the list is filled by an extern service. Maybe I have to convert the list first...

Can someone show me a way to achive my goal? Thanks in advanced.

You should type your list: `List stringArrayList = new java.util.ArrayList<>();` — Djon, May 30 '13 at 09:49
Side note: you can just do `stringArrayList.add(new String[] {"a", "b"});` rather than using your method. — Supericy, May 30 '13 at 09:59
@Supericy yeah you'r right. Sometime lies the easiest things in front of the eyes. So +1 — Reporter, May 30 '13 at 10:28
@Djon When I wrote this post I didn't realized that I worked under 1.4 . sorry for that. — Reporter, May 30 '13 at 10:31
I should have precised that this syntax only works for Java 7, my bad. — Djon, May 30 '13 at 10:32
The diamond inference, I thought that was what OP was talking about. — Djon, May 30 '13 at 10:40

MaheshVarma · Accepted Answer · 2013-05-31T09:35:08.713

Iterator is an interface in java used to iterate over a Collection like ArrayList or other Collection framework classes. Before reading ArrayList make sure values are available using the size() method.

Here a sample working snippet for your problem.

    String [] myArray ;
    if (stringArrayList.size()>0){
        Iterator<String [] > i = stringArrayList.iterator();
        while(i.hasNext()){
                  myArray =  i.next();
                  for(String s : myArray)
                      System.out.println(s);
                }
                }

        }

Don't use Raw ArrayList, instead use Generics

score 1 · Answer 2 · answered May 30 '13 at 09:58

1

Use this:

    List<String[]> stringArrayList = new java.util.ArrayList<String[]>();
    stringArrayList.add(new String[]{"a", "b"});
    stringArrayList.add(new String[]{"c", "d"});

    //if you cant to convert the stringArrayList to an array:
    String[][] listElement = stringArrayList.toArray(new String[0][]);
    for (String[] inArr : listElement){
        for (String e : inArr){
            System.out.print(e + " ");
        }
        System.out.println();
    }

answered May 30 '13 at 09:58

Ahmed KRAIEM

10,267
4
30
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Just a side question: Which conditions speak for to declare the target object as "String[][]"? I've never seen this before. – Reporter May 31 '13 at 09:08
`stringArrayList` is a list of arrays of strings (`List`); converting `stringArrayList` to an array returns an array of arrays of strings, thus `String[][]`. – Ahmed KRAIEM May 31 '13 at 09:20

amicngh · Answer 3 · 2013-05-30T10:07:07.377

0

String[] listElement;

Above statements is incorrect because you are keeping arrays in list so your listElement must contain String[] .

String [][] listElement

Something like below.

listElement=stringArrayList.toArray(new String[stringArrayList.size()][]);

edited May 30 '13 at 10:07

answered May 30 '13 at 09:59

amicngh

7,831
3
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Extract String[] elements from a list

3 Answers3