Introduction to Programming

The API is complete

The final version of our API looks as follows:

public interface Calculator {  int multiplyByTwo(int i);  static Calculator createInstance(){    return  CalculatorFactory.create();  }  static String addOneAndConvertToString(double d){    return  CalculatorFactory.addOneAndConvertToString(d);  }  String CONF_NAME = "calculator.conf";  //file name  String CONF_WHICH_IMPL = "which.impl"; //key in the .conf file  enum WhichImpl{    multiplies, //uses multiplication operation                // and returns addOneAndConvertToString()                 // result without formating    adds    //uses addition operation             // and returns addOneAndConvertToString()            // result with two decimals only  }}

This way, we maintain the single source of record—the interface that captures all the API details. ...