Example - 1

In the following Java example the code performs some complex math when specific test conditions are met. The math is the same in each case and the equations are repeated within the code. Unfortunately if a future change needs to be made then that change needs to be made in all locations. This opens the door to mistakes being made and the changes not being made in the same way in each instance.

// complex math equationssurface_area = pi * r * s + pi * Math.pow(r, 2);

// a complex set of mathsurface_area = pi * r * s + pi * Math.pow(r, 2);
double s = 10.0;double r = 1.0;double pi = 3.14159;double surface_area;if(r > 0.0) {}if(r > 1.0) {}
public static void main(String[] args) {}
public class Main {}

It is recommended to place the complex math into its own function and then call that function whenever necessary.

//complex math equationsdouble pi = Math.PI;double surface_area = pi * r * s + pi * Math.pow(r, 2);return surface_area;
private double ComplexMath(double r, double s) {}

surface_area = ComplexMath(r, s);
surface_area = ComplexMath(r, s);
double s = 10.0;double r = 1.0;double surface_area;if(r > 0.0) {}if(r > 1.0) {}
public static void main(String[] args) {}
public class Main {}