牛码-0001

guava -> Strings.repeat

    char[] array = new char[size];
    string.getChars(0, len, array, 0);
    int n;
    for (n = len; n < size - n; n <<= 1) {
      arraycopy(array, 0, array, n, n);
    }
    arraycopy(array, 0, array, n, size - n);
    return new String(array);