Dynamically extending classes with new methods
One of the exciting characteristics of Groovy is Meta Object Protocol (MOP). In a nutshell, the term metaprogramming refers to writing code that can dynamically change its behavior at runtime. A Meta Object Protocol refers to the capabilities of a dynamic language that enable metaprogramming. In this recipe, we are going to look at one of the capabilities of the MOP, which is ExpandoMetaClass.
Groovy's ExpandoMetaClass lets you assign behavior and state to classes at runtime without editing the original source code; it is essentially a layer above the original class. In the next section of the recipe, we will show you how to achieve such a result.
How to do it...
Adding a new method to a Groovy (or Java) class is straightforward. We are going to perform the following given steps to add a getInEuros method to the BigDecimal Java class in order to convert US dollars to euros:
In a new Groovy script, type the following code:
import java.text.NumberFormat...
