java泛型 - java数组泛型转换

Question

有如下java代码：

<code class="java">// 求两个数组的并集，利用set的元素唯一性
    public static <T> T[] union(T[] arr1, T[] arr2) {
        Set<T> set = new HashSet<>();
        Collections.addAll(set, arr1);
        Collections.addAll(set, arr2);
        return set.toArray(new Object[set.size()]);
    }</code>

问：该段代码报错，提示返回的类型应该是Object[]，怎么才能返回T[]？

Answer 1

return set.toArray(arr1);

toArray()The method is also generic, and the return type is consistent with the parameter type. Yours is an Object array, of course it won’t work.