arraylist and arrays

[k4ghg]

I'm working with arraylists and was wondering how to convert the arraylist to a multi dimensional array. I am collection 12 monthly walues for differnt locations. In the past I had used:

rain [location][month]

Since I dont know the number of locations I'm adding each month to an arraylist. I might have 120 values and I would like to get them back in a for of rain [location] [month]. Any suggestions would be appreciated. Thanks...Ronnie

 

[Diancecht]

Hava a look at the toArray() method.

http://java.sun.com/j2se/1.4.2/docs/api/java/util/ArrayList.html

Cheers,

Dian

 

[k4ghg]

Thanks - I can get the arrayList to a single dimension array, but am having problems doing a 2 dimensional array. I tried an arrayList within an arrayList and it worked, but I could not get the data out. Thanks.

 

[Diancecht]

I'd go for an ArrayList containing 12-length array.

Cheers,

Dian

 

[WyldGynjer]

I was trying to figure this out the other day - I still haven't but the things I've read say that it is not possible - which I don't know if it's true or not.

But one suggestion I saw was to use a HashMap instead of an array list. I was going to explore this option - I just haven't yet.

 

[k4ghg]

Thanks, I'm using an ArrayList because I don't know the number of locations. I read that you can creat an Arraylist of an ArrayList, but the element is a a comma delimited Object that I'm having problems converting.

 

[uolj]

Maybe I am not understanding the problem, but does this example help?

import java.util.ArrayList;

public class TwoDimTest {
  public static void main(String[] args) {
    // Fill the ArrayLists with data and arbitrary sizes.
    ArrayList<ArrayList<String>> originalList = new ArrayList<ArrayList<String>>();
    for (int outerIdx = 0; outerIdx < 5; ++outerIdx) {
      originalList.add(new ArrayList<String>());
      for (int innerIdx = outerIdx; innerIdx >= 0; --innerIdx) {
        originalList.get(outerIdx).add(((Integer)innerIdx).toString());
      }
    }

    // Actually copy the arraylists to the 2-dimensional array.
    int size = originalList.size();
    String [][] twoDStringArray = new String[size][];
    for (int index = 0; index < size; ++index) {
      twoDStringArray[index] = originalList.get(index).toArray(new String[0]);
    }

    // Display to show the values in the arraylists.
    System.out.println("ArrayList Data:");
    for (ArrayList<String> innerArrList : originalList) {
      for (String value : innerArrList) {
        System.out.println(value);
      }
    }
    // Display to show the arrays contain the correct values.
    System.out.println("\nArray Data:");
    for (String[] outer : twoDStringArray) {
      for (String inner : outer) {
        System.out.println(inner);
      }
    }
  }
}

Focus on the second of the four blocks of code. This uses the toArray function that takes an argument to specify the proper type.

 

[k4ghg]

Thanks...I do appreciate your kind suggestions. I'm certain the snipet works. My problem is that I'm still using Java 1.4 and it does not support some of that code.