The criteria pattern

The criteria design pattern provides a clear and concise technique for filtering objects according to set criteria. It can be a very powerful tool as this next exercise will demonstrate.

In this example, we will apply a filter pattern to sort through a list of ingredients and filter them according to whether they are vegetarian and where they are produced:

1. Begin by creating the filter interface, like so:

   public interface Filter { 
    
       List<Ingredient> meetCriteria(List<Ingredient> ingredients); 
   } 
   

2. Next add the ingredient class, like this:

   public class Ingredient { 
    
       String name; 
       String local; 
       boolean vegetarian; 
    
       public Ingredient(String name, String local, boolean vegetarian){ 
           this.name = name; 
           this.local = local; 
           this.vegetarian = vegetarian; 
       } 
    
       public String getName() { 
           return name; 
       } 
    ...