README.md

Today we look at a refactoring that is similar to the Pull Up method. Instead of a method, it is obviously done with a field instead!

public abstract class Account {
   public abstract int getMinimumBalance();
}

public class CheckingAccount extends Account{
   private int minimumAccountBalance = 1000;

   @Override
   public int getMinimumBalance() {
   	return minimumAccountBalance;
   }

}
public class SavingsAccount extends Account {
   private int minimumAccountBalance = 1000;

   @Override
   public int getMinimumBalance() {
   	return minimumAccountBalance;
   }

}

In this example, we have a constant value that is duplicated between two derived classes. To promote reuse we can pull up the field into the base class and rename it for brevity.

public abstract class Account {
	private static final int minimumAccountBalance = 1000;
	public int getMinimumAccountBalance(){
		return minimumAccountBalance;
	}

}

public class CheckingAccount extends Account {
	//minimum balance is available from the parent!

}

public class SavingsAccount extends Account {
	//minimum balance is available from the parent!

}

Original C# code from the book:

public abstract class Account
{
}

public class CheckingAccount : Account
{
    private decimal _minimumCheckingBalance = 5m;
}

public class SavingsAccount : Account
{
    private decimal _minimumSavingsBalance = 5m;
}

public abstract class Account
{
    protected decimal _minimumBalance = 5m;
}

public class CheckingAccount : Account
{
}

public class SavingsAccount : Account
{
}