# Tutorial 3
tags: software systems, se
time: 2025-12-06 07:18:10

```java
public class RentalService {

    // A "God Method" handling everything
    public String processRental(String type, int age, String license, String street, String city, String zip, double basePrice) {
        
        System.out.println("Processing rental for: " + type);

        // 1. Validation Logic (Mixed levels of abstraction)
        if (license == null || license.isEmpty()) {
            return "Error: No License";
        }
        if (age < 18) {
            return "Error: Underage";
        }

        // 2. Pricing Logic (Switch Statements - OO Abuser)
        double finalPrice = 0;
        if (type.equals("E-Bike")) {
            finalPrice = basePrice * 1.1; // 10% tax
            if (age < 25) {
                finalPrice += 5.0; // Insurance surcharge
            }
        } else if (type.equals("Scooter")) {
            finalPrice = basePrice * 1.2;
            if (age < 21) {
                return "Error: Too young for Scooter";
            }
        } else if (type.equals("StandardBike")) {
            finalPrice = basePrice;
        } else {
            return "Error: Invalid Type";
        }

        // 3. Receipt Generation (Feature Envy / Primitive Obsession)
        // Why is RentalService formatting the address? 
        String addressLabel = street + "\n" + city + ", " + zip;
        String receipt = "RENTAL CONFIRMED\n" + addressLabel + "\nPrice: " + finalPrice;
        
        return receipt;
    }
}
```



```java
// Extracted Method
private double calculatePrice(String type, int age, double basePrice) {
    if (type.equals("E-Bike")) {
         return (basePrice * 1.1) + (age < 25 ? 5.0 : 0);
    } 
    // ... rest of logic
    return basePrice;
}
```


```java
// New Abstraction
public class CustomerAddress {
    private String street;
    private String city;
    private String zip;
    
    // Logic moved here (Fixing Feature Envy)
    public String getFormattedLabel() {
        return street + "\n" + city + ", " + zip;
    }
}
```




```java
public class RentalService {
    
    // Complexity dropped to 2 (Base + 1 validation check)
    public String processRental(String type, int age, String license, CustomerAddress addr, double basePrice) {
        
        if (!isValidDriver(license, age, type)) {
             return "Error: Validation Failed";
        }

        double price = calculatePrice(type, age, basePrice);
        
        // Delegating address formatting to the Address object
        return "CONFIRMED\n" + addr.getFormattedLabel() + "\nPrice: " + price;
    }
}
```