Introduction to Spring - Spring Enterprise Recipes: A Problem Solution Approach - page 46

public double kilogramToPound(double kilogram);
public double kilometerToMile(double kilometer);
}
Then you provide an implementation for each interface with println statements to let you know
when the methods are executed.
package com.apress.springenterpriserecipes.calculator;
public class ArithmeticCalculatorImpl implements ArithmeticCalculator {
public double add(double a, double b) {
double result = a + b;
System.out.println(a + " + " + b + " = " + result);
return result;
}
public double sub(double a, double b) {
double result = a - b;
System.out.println(a + " - " + b + " = " + result);
return result;
}
public double mul(double a, double b) {
double result = a * b;
System.out.println(a + " * " + b + " = " + result);
return result;
}
public double div(double a, double b) {
if (b == 0) {
throw new IllegalArgumentException("Division by zero");
}
double result = a / b;
System.out.println(a + " / " + b + " = " + result);
return result;
}
}
package com.apress.springenterpriserecipes.calculator;
public class UnitCalculatorImpl implements UnitCalculator {
public double kilogramToPound(double kilogram) {
double pound = kilogram * 2.2;
System.out.println(kilogram + " kilogram = " + pound + " pound");
return pound;
}