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https://github.com/qkrwoghd04/design_patterns_implementation
try to use various design patterns to implement a simple Console-Based Library Management System(LMS) using java
https://github.com/qkrwoghd04/design_patterns_implementation
console decorator-pattern factory-pattern java library-management-system observer-pattern singleton-pattern
Last synced: about 1 month ago
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try to use various design patterns to implement a simple Console-Based Library Management System(LMS) using java
- Host: GitHub
- URL: https://github.com/qkrwoghd04/design_patterns_implementation
- Owner: qkrwoghd04
- Created: 2024-03-23T07:47:46.000Z (10 months ago)
- Default Branch: main
- Last Pushed: 2024-06-13T05:54:07.000Z (7 months ago)
- Last Synced: 2024-06-13T09:13:10.341Z (7 months ago)
- Topics: console, decorator-pattern, factory-pattern, java, library-management-system, observer-pattern, singleton-pattern
- Language: Java
- Homepage:
- Size: 46.9 KB
- Stars: 0
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
## Console-Based Library Management System(LMS)
### 1. How to run java code on cmd
### Step 1:
#### Compile whole java classes in library package
### Step 2:
#### Using "-cp ." command
#### When using the "-cp ." option, it instructs the Java runtime environment to include the current directory in the classpath. This allows Java programs to recognize and use .class files located in the current directory
### 2. Design Patterns for LMS
### Singleton Pattern for Database class
```Java
// The DatabaseConnection class implements the Singleton Design Pattern.
// It ensures that only one instance of the DatabaseConnection class can exist.
public class DatabaseConnection {
private static DatabaseConnection instance;
private Map users;
private Map books;
private Map> userBorrowedBooks = new HashMap<>();
private Map borrowedDates = new HashMap<>();
private DatabaseConnection() {
users = new HashMap<>();
books = new HashMap<>();
userBorrowedBooks = new HashMap<>();
}
public static DatabaseConnection getInstance() {
if (instance == null) {
instance = new DatabaseConnection();
}
return instance;
}
```
### Factory Pattern for User class
```Java
// The UserFactory class implements the Factory Design Pattern.
// It provides a static method to create objects of User subclasses (Student or Faculty) based on the type parameter.
class UserFactory{
// This static method creates and returns User objects.
// The type of User object (Student or Faculty) depends on the type argument.
public static User createUser(String type, String name, String phoneNum){
switch(type.toLowerCase()){
case "student":
return new Student(name, phoneNum);
case "faculty":
return new Faculty(name, phoneNum);
default:
throw new IllegalArgumentException("Unknown user type.");
}
}
}
```
### Decorator Pattern for managing **overdue books**
```Java
// BookDecorator class serves as a decorator for the Book class. It follows the Decorator Pattern,
// allowing dynamic addition of new behaviors (in this case, tracking overdue status) to Book objects.
public class BookDecorator {
private Book book;
private boolean isOverdue;
// Constructor wraps a Book object, enabling dynamic extension of its behavior without modifying the original class
public BookDecorator(Book book) {
this.book = book;
this.isOverdue = false;
}
public void setOverdue(boolean isOverdue) {
this.isOverdue = isOverdue;
}
```
### Observer Pattern for state changes
```Java
// The Observer interface declares the update method that is called by the subject.
// Observers implement this interface to react to changes in the subject's state.
public interface Observer {
void update(String availability);
}
// The Subject interface declares a set of methods for managing observers.
// It allows subjects to register, remove, and notify observers about the state changes.
public interface Subject {
void registerObserver(Observer o);
void removeObserver(Observer o);
void notifyObservers();
}
```