Arrays.copyofRange()函數

public static int[] copyOfRange(int[] original, int from, int to) {
    int newLength = to - from;
    if (newLength < 0)
        throw new IllegalArgumentException(from + " > " + to);
    int[] copy = new int[newLength];
    System.arraycopy(original, from, copy, 0,
                     Math.min(original.length - from, newLength));
    return copy;
}

copyofRange()函數先將要複製的數組的大小進行計算，然後創建一個該大小的數組，利用arraycopy從from複製數組大小個的數據到新數組中，然後返回該數組，所以如果要複製數組的0到n的話必須寫的是0到n+1