val a = Array(1,2,3)
a(1)
这里的a(1)应该是调用class Array的apply方法
我在源码中并没有看到具体的实现在哪里，请问这里获取数据是怎么实现的!

  /** The element at given index.
   *
   *  Indices start at `0`; `xs.apply(0)` is the first element of array `xs`.
   *  Note the indexing syntax `xs(i)` is a shorthand for `xs.apply(i)`.
   *
   *  @param    i   the index
   *  @return       the element at the given index
   *  @throws       ArrayIndexOutOfBoundsException if `i < 0` or `length <= i`
   */
  def apply(i: Int): T = throw new Error()