I have a list like this:
List<MyObject[]> list= new LinkedList<MyObject[]>(); and on Object like this:
MyObject[][] myMatrix; How can I assign the "list" to "myMatrix"?
I don't want to loop over the list and assign element by element to MyMatrix, but I want to assign it directly (with the oppurtune modifications) if possible. Thanks
You could use toArray(T[]).
import java.util.*; public class Test{ public static void main(String[] a){ List<String[]> list=new ArrayList<String[]>(); String[][] matrix=new String[list.size()][]; matrix=list.toArray(matrix); } } 
The following snippet shows a solution:
// create a linked list List<String[]> arrays = new LinkedList<String[]>(); // add some trivial test data (note: arrays with different lengths) arrays.add(new String[]{"a", "b", "c"}); arrays.add(new String[]{"d", "e", "f", "g"}); // convert the datastructure to a 2D array String[][] matrix = arrays.toArray(new String[0][]); // test output of the 2D array for (String[] s:matrix) System.out.println(Arrays.toString(s)); Let us assume that we have a list of 'int' array.
List<int[]> list = new ArrayList(); Now to convert it into 2D array of type 'int', we use 'toArray()' method.
int result[][] = list.toArray(new int[list.size()][]); We can generalize it further like-
List<T[]> list = new ArrayList(); T result[][] = list.toArray(new T[list.size()][]); Here, T is the type of array.
Use toArray() or toArray(T[]) method of LinkedList.
You can do it like this:
public static void main(String[] args) { List<Item[]> itemLists = new ArrayList<Item[]>(); itemLists.add(new Item[] {new Item("foo"), new Item("bar")}); itemLists.add(new Item[] {new Item("f"), new Item("o"), new Item("o")}); Item[][] itemMatrix = itemLists.toArray(new Item[0][0]); for (int i = 0; i < itemMatrix.length; i++) System.out.println(Arrays.toString(itemMatrix[i])); } Output is
[Item [name=foo], Item [name=bar]] [Item [name=f], Item [name=o], Item [name=o]] assuming that Item is as follows:
public class Item { private String name; public Item(String name) { super(); this.name = name; } @Override public String toString() { return "Item [name=" + name + "]"; } } Converto list to array using. List.Array()
Then Use System.arraycopy to copy to the 2d array works well for me
Object[][] destination = new Object[source.size()][]; System.arraycopy(source, 0, destination, 0, source.size()); 