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Why isn't the throw working?

I am trying to do this

List<String> stringList = new ArrayList<String>();
stringList.add("one");
stringList.add("two");
stringList.add("three");

(String[]) stringList.toArray();

why is this giving me a cast class exception?

Caused by: java.lang.ClassCastException: [Ljava.lang.Object;
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5 answers


Better try this other method:

String[] stringArray = stringList.toArray(new String[stringList.size()]);


This way the returned array is of the exact type you want, no casting is required. The method you are calling returns Object[]

, not String[]

, and the action you are trying to do is invalid.

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The reason your code crashes is because it .toArray()

returns an array of type Object[]

that cannot be cast into String[]

. To fix this use another toArray(T[] a)

ie



stringList.toArray(new String[0]);

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Since the toArray()

class method List

returns Object[]

not String[]

, and you cannot cast from Object[]

to String[]

. However, the correct way to do it is:

String[] array = new String[stringList.size()];
stringList.toArray(array);

or

String[] array = stringList.toArray(new String[stringList.size());
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You cannot use a String array. Do you want to:

String [] test = stringList.toArray (new String [stringList.size ()]);

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The method ArrayList<T>.toArray()

returns an array of type Object

, since this is a perfectly acceptable thing. In fact, due to the erasure of the styles, this is the only thing it can do.

If you want to get an array of type String

, call the method ArrayList<T>.toArray(T[])

. In your case, you would call it like this:

stringList.toArray(new String[3]);

A call of this type will contain the content ArrayList

in the presented array String

.

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