How to convert ArrayList<String[]> to multidimensional array String[][]?

Question

I have a collection of String[] values, for example:

ArrayList<String[]> values = new ArrayList<>();

String[] data1 = new String[]{"asd", "asdds", "ds"};
String[] data2 = new String[]{"dss", "21ss", "pp"};

values.add(data1);
values.add(data2);

And I need convert this to multidimensional array String[][]. When I try this:

String[][] arr = (String[][])values.toArray();

I get a ClassCastException.

How can I solve this problem?

Community · Accepted Answer · 2021-06-12 03:20:02Z

7

What about this (this does not require Java 11 while toArray(String[][]::new) requires)

values.toArray(new String[0][0]);

That method is:

/**
 * Returns an array containing all of the elements in this list in proper
 * sequence (from first to last element); the runtime type of the returned
 * array is that of the specified array.  If the list fits in the
 * specified array, it is returned therein.  Otherwise, a new array is
 * allocated with the runtime type of the specified array and the size of
 * this list.

edited Jun 12, 2021 at 3:20

CommunityBot

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answered Feb 14, 2021 at 11:48

ch271828n

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Youcef LAIDANI · Accepted Answer · 2021-02-14 11:48:58Z

4

No don't need to cast, check the doc, you can just use:

String[][] arr = values.toArray(new String[0][]);

Or if you are using Java 11

String[][] arr = values.toArray(String[][]::new);

answered Feb 14, 2021 at 11:48

Youcef LAIDANI

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