Java泛型和Array的 [英] Java generics and Array's

问题描述

下面的代码片段在我的单元测试中运行时有意义。我在标有'>>>>'的行上得到一个ClassCastException（对象不能转换为字符串）。这种类型的操作可以通用吗？

The following snippet makes sense yet when I run this against my unit test.. I get a ClassCastException (Object can't be cast to String) on the line marked with '>>>>'. Can this type of operation be done in a generic ?

public class ArrayUtils<E> {

    public static <E> E[] appendToArray(E[] array, E item) {
        E[] result = (E[])new Object[array.length+1];
        for(int i=0; i < array.length; i++ ) {
            result[i] = array[i];
        }
        result[result.length-1] = item;
        return result;
    }

}

   @Test
   public void testAppendToArray() {
       String[] array = new String[1];
       array[0] = "a";

       assertSame("Array is not correct length.", 1, array.length );
>>>>   String[] appendToArray = ArrayUtils.<String>appendToArray(array, "b");
       assertSame("Array is not correct length.", 2, appendToArray.length );
    }

推荐答案

你不应该创建你的数组使用新的Object []。您应该使用 Array.newInstance（Class clazz，int length）来代替。

You should not create your array using new Object[]. You should use Array.newInstance(Class clazz, int length) instead.

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