Java – how does arraybuffer work in memory?

I want to use arraybuffer in my program to save a list of numbers I want to use it as a queue Delete the first item in the list each time and use it Then I want to know that every time the first item is deleted, all the other numbers in the queue move one place I mean, can I read the item (0) again next time?

Solution

If you look at Scala source code or arraybuffer, you will see the following implementation of remove:

/** Removes the element on a given index position. It takes time linear in
   *  the buffer size.
   *
   *  @param n       the index which refers to the first element to delete.
   *  @param count   the number of elements to delete
   *  @throws Predef.indexoutofboundsexception if `n` is out of bounds.
   */
  override def remove(n: Int,count: Int) {
    require(count >= 0,"removing negative number of elements")
    if (n < 0 || n > size0 - count) throw new indexoutofboundsexception(n.toString)
    copy(n + count,n,size0 - (n + count))
    reduceToSize(size0 - count)
  }

Therefore, the deleted elements will no longer exist in the array, but in fact, deletion means copying all elements (shift in the definition), which will be slow for longer arrays