Java code: data structures, algorithms, and OOP.
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# Lists
## Abstract List Type
The list abstract data type (ADT) implements the following methods:
* size
* isEmpty
* first
* last
* addFirst
* addLast
* removeFirst
Other convenience methods:
* remove
* removeFirst
* removeLast
* removeElement
## Mistakes Learnings Tricks
Use the `Integer` class when processing integers!
When you have a String and you want an integer:
* Integer.parse("525")
When you have an integer and you want a String:
* Integer.toString(str)
In general, you can also use the String class to turn the object into a String:
* `String.valueOf(o)`
Linked List specific details:
* Need to handle cases where you are adding to an empty list, or removing last item from list
* Especially when using tail pointer, be aware of what it is pointing to and when it needs to be updated.
Linked list methods should automatically become a list of bookkeeping things to do.
* Add method: consider adding to an empty list, non-empty list
* Add at index i:
* What are all possible cases?
* i is too big, i is too small
* the list is empty
* i is a special case
* how can we fold any of these cases into other cases (list empty -> i too small)
Size of linked list:;
* Number of bytes:
* See [https://charlesreid1.com/wiki/Java/Memory](https://charlesreid1.com/wiki/Java/Memory)
* 8 bytes per reference to memory (64 bit)
* 16 bytes of object overhead
* Size estimation:
* 1000-integer linked list should theoretically use up:
* 1000 nodes x ( 4 bytes per integer + 8 bytes per ref + 16 bytes object overhead )
* 28,0000 bytes ~ 28 kB
* What's the power of 2 that would correspond to that?
* 1000 integers ~ 1024 integers ~ 2^10 integers
* Round it up to 8 bytes per integer, 8 bytes per ref, 16 bytes per object overhead)
* 2^5 = 32 bytes per integer
* 32 x 8 = 2^5 * 2^3 = 2^8 = 256 bits = 256 zeroes and ones
* 10 GB / 10 kB/obj = 10x10^6 / 10 = 10^6
Exceptions:
```
class Empty extends Exception{};
```
Circular linked list:
* Take care with the details of pointers.
Doubly linked list:
* It makes algorithms easier, but
Nice link explaining sizes of Strings in memory:
* https://stackoverflow.com/a/18030595
```
sizeof(string) =
8 + // object header used by the VM
8 + // 64-bit reference to char array (value)
8 + string.length() * 2 + // character array itself (object header + 16-bit chars)
4 + // offset integer
4 + // count integer
4 + // cached hash code
```
Timing:
* Don't do logarithmic size.........
* Need to fix that actually.
* Cover a single order of magnitude, then maybe try for two.