jay/notes
1
0 Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Tidy up

Browse Source
This commit is contained in:
John Gatward committed 2026-10-04 15:24:17 +01:00
1 parent d0f27f276b
commit d6f54d4ec2
103 files changed
+3663 -3779
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

docs/lectures/dms/01_java_collections.md
+31 -22
View File
@@ -4,24 +4,28 @@ Week 3 (Oct 5th)
**Part 1**
In java a *collection* is an object that represents a group of objects.
In Java, a *collection* is an object that represents a group of objects.
The collections API is a unified framework for representing and manipulating collections independently of their implementation.
An *API* (application programming interface) is an interface protocol between a client and a server, intended to simplify the client side software.
An *API* (application programming interface) is an interface protocol between a client and a server, intended to simplify the client-side software.
A *library* contains re-usable chunks of code.
A *library* contains reusable chunks of code.
**Java Collections framework**
- We have container objects that contain objects
- All containers are either "collections" or "maps"
- All containers provide a common set of method signatures, in addition of their unique set of method signatures
- All containers provide a common set of method signatures, in addition to their unique set of method signatures
*Collection* - Something that holds a dynamic collection of objects
*Map* - Defines mapping between keys and objects (two collections)
*Iterable* - Collections are able to return an iterator objects that can scan over the contents of a collection one object at a time
NOTE: Vector is a legacy structure in Java replaced with *ArrayList*
Stack is now *ArrayDeque*
*Map* - Defines mapping between keys and objects (two collections)
*Iterable* - Collections are able to return an iterator object that can scan over the contents of a collection one object at a time
NOTE: Vector is a legacy structure in Java replaced with *ArrayList*.
Stack is now *ArrayDeque*.
`LinkedList(Collection<? extends E> c)` - means some type that either is E or a subtype of E. The `?` is a wildcard.
@@ -34,7 +38,7 @@ public static void main(String[] args) {
}
```
This is bad coding practice, the collection constructor are not able to specify the type of objects the collection is intended to contain. A `ClassCastException` will be thrown if we attempt to cast the wrong type.
This is bad coding practice: the collection constructor does not specify the type of objects the collection is intended to contain. A `ClassCastException` will be thrown if we attempt to cast to the wrong type.
```java
public static void main(String[] args) {
@@ -45,13 +49,15 @@ public static void main(String[] args) {
}
```
This is a type safe collection using generics.
This is a type-safe collection using generics.
- Classes support generics by allowing a type variable to be included in their declaration.
- The `<>` show the same type as stated (in this case string)
- You cannot type a collection with a primitive data type eg int
- The `<>` indicate the same type as stated (in this case `String`)
- You cannot type a collection with a primitive data type, e.g. `int`
**HashMap Class**
- A HashMap is a hash table based implementation of the map interface. This implementation provides all if the optional map operations, and permits null values and the null key.
- A HashMap is a hash-table-based implementation of the map interface. This implementation provides all of the optional map operations and permits null values and the null key.
```java
public static void main(String[] args) {
@@ -79,7 +85,7 @@ Millie = 17
__Relationships between objects__
*Aggregation* - The object exists outside the other. It is created outside so it is passed as an argument.
An animal object *is part of* a compound object (semantically) but the animal object can be shared and if the compound object is deleted, the animal object isn't deleted.
An animal object *is part of* a compound object (semantically), but the animal object can be shared. If the compound object is deleted, the animal object isn't deleted.
```java
public class Compound {
@@ -93,7 +99,7 @@ public class Compound {
![Image](assets/1.png)
*Composition* - The object only exists if the parent object exists, if the parent object is deleted then so is the child object.
*Composition* - The object only exists if the parent object exists. If the parent object is deleted, then so is the child object.
The zoo object owns the compound object. If the zoo object is deleted then the compound object is also deleted.
```java
@@ -105,11 +111,13 @@ public class Zoo {
![Image](assets/2.png)
**Inheritance**
A way of forming new classes based on existing classes. Has a "is-a" relationship.
*Polymorphism* - A concept in object oriented programming. Method overloading and method overriding are two types of polymorphism.
A way of forming new classes based on existing classes. Has an "is-a" relationship.
*Polymorphism* - A concept in object-oriented programming. Method overloading and method overriding are two types of polymorphism.
- *Method Overloading* - Methods with the same name co-exist in the same class but they must have different method signatures. Resolved during compile time (static binding).
- *Method Overriding* - Methods with the same name is declared in parent and child class. Resolved during runtime (dynamic binding).
- *Method Overriding* - Methods with the same name are declared in parent and child classes. Resolved at run time (dynamic binding).
```java
public class Child extends Parent {
@@ -124,12 +132,13 @@ public class Child extends Parent {
}
```
The super keyword called the parent class' constructor.
The `super` keyword calls the parent class's constructor.
![Image](assets/3.png)
**What is the difference between an abstract class and an interface**
- Java abstract class can have instance methods that implement a default behaviour. May contain non-final variables.
**What is the difference between an abstract class and an interface?**
- A Java abstract class can have instance methods that implement a default behaviour. It may contain non-final variables.
- Java interfaces have methods that are implicitly abstract and cannot have implementations. Variables are declared final by default.
Interfaces are less restrictive when it comes to inheritance, interfaces can have many levels of inheritance where as a class can only have one level.
Interfaces are less restrictive when it comes to inheritance: interfaces can have many levels of inheritance, whereas a class can only have one level.
docs/lectures/dms/02_uml.md
+87 -92
View File
@@ -1,92 +1,87 @@
# Unified Modelling Language
12/10/20
**UML**: A specification defining a graphical language for visualising, specifying, constructing and documenting the artefacts of distributed object systems.
Latest version: **2.6**
**Benefits of UML**
- Enhances communication and ensures the right communication
- Captures the logical software architecture independent of the implementation language.
- Helps to manage the complexity
- Enables reuse of design
<img src="assets/4.png" alt="img" style="zoom:80%;" />
## Object Orientated Analysis
**Use case diagrams**
- Describe a set of actions that some system should or can perform in collaboration with one or more external users of the system.
- No attempt to represent an order or a number of executions.
**Use case diagram components**
`Actors` - Entities that interface with the system. Can be people or other systems.
`Use case` - Based on user stories and represent what the actor wants your system to do for them. In the use case diagram only the use case name is represented.
`Subject` - Classifier representing a business, software system, physical system or device under analysis design, or consideration.
`Relationships`
> Relationships between use case and actor
>
> 1. Association indicates which actor indicates which use case
>
> Relationship between two use cases
>
> 1. Specifying common functionality and simplifying use case flows
> 2. Using <<include>> or <<extend>>
**`<<include>>`**- multiple use cases share a piece of same functionality which is placed in a separate use case.
**`<<extend>>`** - Used when activities might be performed as part of another activity but are not mandatory for a use case to run successfully.
**Use case diagram of a fleet logistics management company**
![image](assets/5.png)
**Base Path** - The optimistic path (best case scenario)
**Alternative Path** - Every other possible way the system can be used/abused. Includes perfectly normal alternate use, but also errors and failures.
Use Case: `Borrow copy of book`
> **Purpose**: The book borrower (BB) borrows a book from the library using the Library Booking System (LBS)
>
> **Pre-conditions**:
>
> 1. The book must exist
> 2. The book must be available
>
> **Base Path**:
>
> 1. LBS requests membership card
> 2. BB provides membership card
> 3. BB is logged in by LBS
> 4. LBS checks permissions / debts
> 5. LBS asks for presenting a book
> 6. BB presents a book
> 7. LBS scans RFID tag inside book
> 8. LBS updates records accordingly
> 9. LBS disables anti-theft device
> 10. BB is logged out by LBS
> 11. LBS confirms that process has been completed successfully
>
> **Alternative Path**
>
> 1. BB's card has expired: Step 3a: LBS must provide a message that card has expired; LBS must exit the use case
>
> **Post conditions for base path**
>
> **Base path** - BB has successfully borrowed the book & system is up to date.
>
> **Alternate Path 1** - BB was NOT able to borrow the book & system is up to date.
# Unified Modelling Language
12/10/20
**UML**: A specification defining a graphical language for visualising, specifying, constructing and documenting the artefacts of distributed object systems.
Latest version: **2.6**
**Benefits of UML**
- Enhances communication and ensures the right communication
- Captures the logical software architecture independent of the implementation language.
- Helps to manage the complexity
- Enables reuse of design
<img src="assets/4.png" alt="img" style="zoom:80%;" />
## Object Orientated Analysis
**Use case diagrams**
- Describe a set of actions that some system should or can perform in collaboration with one or more external users of the system.
- No attempt to represent an order or a number of executions.
**Use case diagram components**
`Actors` - Entities that interface with the system. Can be people or other systems.
`Use case` - Based on user stories and represents what the actor wants your system to do for them. In the use case diagram, only the use case name is represented.
`Subject` - Classifier representing a business, software system, physical system or device under analysis, design or consideration.
`Relationships`
> Relationships between use case and actor
>
> 1. Association indicates which actor indicates which use case
>
> Relationship between two use cases
>
> 1. Specifying common functionality and simplifying use case flows
> 2. Using <<include>> or <<extend>>
**`<<include>>`** - Multiple use cases share a piece of the same functionality, which is placed in a separate use case.
**`<<extend>>`** - Used when activities might be performed as part of another activity but are not mandatory for a use case to run successfully.
**Use case diagram of a fleet logistics management company**
![image](assets/5.png)
**Base Path** - The optimistic path (best case scenario)
**Alternative Path** - Every other possible way the system can be used/abused. Includes perfectly normal alternate use, but also errors and failures.
Use Case: `Borrow copy of book`
> **Purpose**: The book borrower (BB) borrows a book from the library using the Library Booking System (LBS)
>
> **Pre-conditions**:
>
> 1. The book must exist
> 2. The book must be available
>
> **Base Path**:
>
> 1. LBS requests membership card
> 2. BB provides membership card
> 3. BB is logged in by LBS
> 4. LBS checks permissions / debts
> 5. LBS asks the borrower to present a book
> 6. BB presents a book
> 7. LBS scans RFID tag inside book
> 8. LBS updates records accordingly
> 9. LBS disables anti-theft device
> 10. BB is logged out by LBS
> 11. LBS confirms that process has been completed successfully
>
> **Alternative Path**
>
> 1. BB's card has expired: Step 3a: LBS must provide a message that card has expired; LBS must exit the use case
>
> **Postconditions for base path**
>
> **Base path** - BB has successfully borrowed the book and the system is up to date.
>
> **Alternative Path 1** - BB was NOT able to borrow the book and the system is up to date.