Java 带有增强for循环的ClassCastException

灵感来源于一个问题，当时我正在摆弄一个实验性的收藏品：

/**
 * Pretends to be a Collection of samples from the items.
 *
 * @param <T>
 */
class Samples<T> extends AbstractCollection<T[]> implements Collection<T[]> {

    private final int of;
    private final T[] items;

    public Samples(int of, T... items) {
        this.of = of;
        this.items = items;
    }

    @Override
    public int size() {
        // I know this is wrong.
        return items.length * of;
    }

    @Override
    public Iterator<T[]> iterator() {
        // Make the iterator on the fly.
        return new Iterator<T[]>() {
            // Start at the beginning.
            int which = 0;

            @Override
            public boolean hasNext() {
                // That's how many there are.
                return which < size();
            }

            @Override
            public T[] next() {
                // Make my new one by cloning the original.
                T[] next = Arrays.copyOf(items, of);
                // Pick the items with reference to which.
                int count = which;
                for (int i = 0; i < of; i++) {
                    // count mod length is the next one to use.
                    next[i] = items[count % items.length];
                    // Used that now.
                    count /= items.length;
                }
                // Consumed that one.
                which += 1;
                return next;
            }

        };

    }

}

public void test() {
    Samples<String> samples = new Samples(4, "A", "B", "C", "D", "E");
    // Walk it with an iterator.
    Iterator<String[]> i = samples.iterator();
    while (i.hasNext()) {
        System.out.println(Arrays.toString(i.next()));
    }
    // Walk it using enhanced for loop.
    for (String[] s : samples) { // Line 91 - error thrown here.
        System.out.println(Arrays.toString(s));
    }
}

是否有什么东西我错过了——也许是咖啡不够

请忽略不正确的

size

方法-我确信这不是问题的原因

---

PS:jdk=jdk1.8.0_11，但使用jdk1.7.0_65仍然失败

您实例化了一个原始类型的

样本

，因此

样本。在您的情况下，

项的类型将是

对象[]

而不是

字符串[]

。在

test（）

方法中：

Samples<String> samples = new Samples(4, "A", "B", "C", "D", "E");

Samples-Samples=新样本（4，“A”、“B”、“C”、“D”、“E”）；

将其更改为：

// Note the diamond operator: <>
Samples<String> samples = new Samples<>(4, "A", "B", "C", "D", "E");

//注意菱形运算符：
样本=新样本（4，“A”、“B”、“C”、“D”、“E”）；

---

作为旁注：在

示例

类中，您不需要声明您实现了

集合

，因为

抽象集合

已经实现了。

异常的确切来源是什么？Stacktrace？@icza-在为（字符串[]s:samples）{读取

的行上。
// Note the diamond operator: <>
Samples<String> samples = new Samples<>(4, "A", "B", "C", "D", "E");