为什么 DefaultListModel.toArray() 会抛出

Question

我正在尝试将DefaultListModel内容复制到数组中。以下行导致异常

testArray = (cGenIndicator[]) indObjList.toArray();

void testCasting() {

    DefaultListModel<cGenIndicator> indObjList;

    indObjList = new DefaultListModel<cGenIndicator>();

    indObjList.addElement(new cGenIndicator(null, null));

    cGenIndicator[] testArray;

    try {

        // This line causses exception saying

        // [Ljava.lang.Object; cannot be cast to [LIndicator.cGenIndicator;

        testArray = (cGenIndicator[]) indObjList.toArray();

    } catch(Exception e) {

        test++;

    }

    test++;

}

Answer 1

toArray, 没有参数, 将返回一个Object[], 不能转换为 a cGenIndicator[]。相反，您可以使用重载方法获取要填充的数组作为参数：testArray = indObjList.toArray(new cGenIndicator[indObjList.size()]);编辑：DefaultListModel没有这个重载方法，Mia Kulpa。将 an 转换Object[]为 a 的一种方法cGenIndicator是使用流：testArray = Arrays.stream(indObjList.toArray())&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .map(cGenIndicator.class::cast)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .toArray(cGenIndicator[]::new)

Answer 2

DefaultListModel.toArray返回Object[]，并且Object[]不能cGenIndicator[]直接转换为。您可以通过以下方式实现：Object[] objectArray = defaultListModel.toArray();int length = objectArray.length;cGenIndicator[] testArray = new cGenIndicator[length];System.arraycopy(objects, 0, testArray, 0, length);