The method getInstance() is undefined for the type ConnectionPool

As an AI language model, I cannot see the entire code, but I'll try my best to explain this error.

This error occurs when a method, in this case, getInstance(), is called on a type that does not have that method defined. In your case, it seems that the type ConnectionPool does not have a method called getInstance().

To fix this error, you need to make sure that the ConnectionPool class has a method called getInstance(). If it does not, you can create one that returns an instance of the ConnectionPool class.

Here's an example code snippet that demonstrates how to create a getInstance() method for the ConnectionPool class:

public class ConnectionPool {
  private static ConnectionPool instance;

  private ConnectionPool() {
    // private constructor to prevent direct instantiation
  }

  public static ConnectionPool getInstance() {
    if (instance == null) {
      instance = new ConnectionPool();
    }
    return instance;
  }

  // other methods and properties of the ConnectionPool class
}

In this code, the getInstance() method is defined as a static method that returns an instance of the ConnectionPool class. The method checks if an instance of the class already exists, and if not, it creates one and returns it. This ensures that only one instance of the ConnectionPool class is created and used throughout the application.