SE450: Strategy: Code [11/22]

SalesOrder, the Context

package example.strategy;

public class SalesOrder {

    // makes a bogus sales order and returns the tax
    public double calcTax() {
	String item1 = "book";
	String item2 = "gum";
	double item1qty = 2;
	double item2qty = 4;
	double item1price = 14.32;
	double item2price = 0.34;
	double totalTax = 0.0;
	
	CalcTax taxer = Configuration.getTaxer();

	totalTax += taxer.taxAmount(item1, item1qty, item1price);
	totalTax += taxer.taxAmount(item2, item2qty, item2price);

	return totalTax;
    }
}
            

CalcTax, the Strategy

package example.strategy;

public interface CalcTax {

    public double taxAmount(String item, double qty, double price);

}
            

USTax, CanTax = ConcreteStrategies

package example.strategy;

public class USTax implements CalcTax {

    public double taxAmount(String item, double qty, double price) {

	// crude algorithm
	if("book".equals(item)) {
	    return qty * price * 0.04;
	} else {
	    return qty * price * 0.05;
	}
    }

}
package example.strategy;

public class CanTax implements CalcTax {

    public double taxAmount(String item, double qty, double price) {

	// crude algorithm, Canada much more expensive than US!
	if("book".equals(item)) {
	    return qty * price * 0.4;
	} else {
	    return qty * price * 0.5;
	}
    }

}

            

Others: Configuration

package example.strategy;

public class Configuration {

    // default to US
    private static CalcTax taxer = new USTax();

    public static CalcTax getTaxer() {
	return taxer;
    }

    public static void setTaxer(String name) {
	if("can".equals(name)) {
	    taxer = new CanTax();
	} else {
	    taxer = new USTax();
	}
    }

}
    

TaskController: the driver

package example.strategy;

package example.strategy;

public class TaskController {

    public static void main(String args[]) {

	SalesOrder order = new SalesOrder();

	Configuration.setTaxer("us");
	System.out.println("The tax for the U.S. is " + 
			   order.calcTax());

	Configuration.setTaxer("can");
	System.out.println("The tax for Canada is " + 
			   order.calcTax());
 
    }

}