CODEWITHSUNDEEP
javaarraylistmultidimensional-arraycollectionsclasscastexception
stfxc
stfxc

Reputation: 174

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

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?

Upvotes: 5

Views: 393

Answers (2)

ch271828n
ch271828n

Reputation: 17567

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.

Upvotes: 7

Youcef LAIDANI
Youcef LAIDANI

Reputation: 59950

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);

Upvotes: 4

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