[docs]: Javadoc Documentation for Utility Classes

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## Description

- **Detailed Description:**
The `PortfolioInfo` class contains essential utility methods (e.g., calculating total portfolio value and distribution), but it lacks descriptive documentation. This can confuse new developers or students trying to understand the purpose and usage of these methods.
- **How to Solve:**
1. **Add Javadoc Comments:**
For each method in `PortfolioInfo`, add a Javadoc comment that describes its purpose, parameters, and return value. For example:
```java
/**
* Calculates the total portfolio value by summing the product of current price and quantity for each stock.
*
* @param stocks List of Stock objects
* @return The total portfolio value as a double
*/
public static double calculateTotalPortfolioValue(List stocks) { ... }
```
2. **Repeat for All Public Methods:**
Ensure that every public method in all utility classes is well documented.
3. **Generate Documentation:**
Optionally, generate the Javadoc HTML pages to verify that the documentation is clear.

Start by locating the PortfolioInfo class and reviewing its public utility methods, then inspect the other utility classes named by the issue. Add Javadoc describing each public method’s purpose, parameters, and return value. Done means the public utility API is documented; optionally generate the Javadoc HTML pages to check the result.

Written by the indexing model from the issue text.