从Object []到String []的转换给出了ClassCastException

Question

The getStrings() method is giving me a ClassCastException . Can anyone tell me how I should get the model? Thanks!

public class HW3model extends DefaultListModel<String>
{           
    public HW3model()
    {
        super();
    }

    public void addString(String string)
    {
        addElement(string);
    }

    /**
     * Get the array of strings in the model.
     * @return
     */
    public String[] getStrings()
    {
         return (String[])this.toArray();
    }
}    

Answer 1

The value returned by toArray is an Object array.

That is, they've be declared as Object[] , not String[] , then returned back via a Object[] .

This means you could never case it to String array, it's simply invalid.

You're going to have to copy the values yourself...for example

public String[] getStrings()
    Object[] oValues= toArray();
    String[] sValues = new String[oValues.length];
    for (int index = 0; index < oValues.length; index++) {
        sValues[index] = oValues[index].toString();
    }
    return sValues;
}

Answer 2

You can't cast one array into the type of another, so you'd have to ensure that you create your own array:

public String[] getStrings() {
    String[] result = new String[getSize()];
    copyInto(result);
    return result;
}

Answer 3

试试这个，看看是否可行

String[] stringArrayX = Arrays.copyOf(objectArrayX, objectArrayX.length, String[].class);