CS61B Proj1A notes

CS61B UCBerkeley java

When writing LinkedListDeque.java, I ran into some prolems. The given API says things like:
public void addFirst(Item): Adds an item to the front of the Deque.
public void addLast(Item): Adds an item to the back of the Deque.
I didn't get what does Item mean here, should I just write exactly Item or should I replace it withString or int?
I got compiler errors when I wrote Item, so I replaced it with String since the LinkedListDequeTest.java first created a new LinkedListDeque of strings(line 40).

However, I got compiler error again as follows:

Then I asked people in wechat study group for help, and they helped me out with this problem. I added<Item> after the class name to meet the requested generic type as follows:

public class LinkedListDeque<Item>{
  private class Node<Item>{
    Item item;
    Node next, prev;

But this is not enough, I had to add<Item> to other places as well:

  private int size;
  private Node <Item> sentinel, last;

 public <Item> Item removeFirst(){
    if(sentinel.next == null){
        return null;
    }
    Item item = <Item> sentinel.next.item;
    sentinel.next = sentinel.next.next;
    size -= 1;
    return item;
  }

  public <Item> Item removeLast(){
    Item item = (Item)last.item;
    last = last.prev;
    last.next = sentinel;
    size -= 1;
    return item;
  }

Seems like I added <Item> to every related class and method, especially I used (Item) for casting. This caused a whitle and finally got some help from the wechat study group.

Later, I was stuck by a problem:

I searched the webs for help, most of the talks were about mistakes in the number of }, some were about GBK and UTF-8. Ironcally, I spent almost half a day finding where went wrong but in vain. Looking back, i guess i was just pissed off and didn't have patience. So, this is a good practice when you are faced with a unknown problem, just stay patient and carefully analyze it.

It turned out I added an extra } when testing parts of the program, and I forgot to delete it when wrote some new parts.

Great, finally things went on well.

ArrayDeque

I ran into problems when writing resize() method for ArrayDeque.java.