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());
