解释器模式

解释器模式（Interpreter Pattern）提供了评估语言的语法或表达式的方式，它属于行为型模式。这种模式实现了一个表达式接口，该接口解释一个特定的上下文。这种模式被用在 SQL 解析、符号处理引擎等。

示例演示：

1. 创建一个生物接口，并提供一个判断的方法

   package test.interpreter;
   /**
    * 所有生物的标识
    */
   public interface Organism {
   
       public boolean isOrganism(String context);
   }

2. 创建一个people实体类

   package test.interpreter;
   
   public class People implements Organism {
       private String data;
   
       public People(String data) {
           this.data = data;
       }
   
       @Override
       public boolean isOrganism(String context) {
           if (context.contains(data)) {
               return true;
           }
           return false;
       }
   }

3. 分别编写两个判断是否是people的实体，一个是或，一个是且

   package test.interpreter;
   
   public class OrPeople implements Organism {
       private Organism org1 = null;
       private Organism org2 = null;
   
       public OrPeople(Organism org1, Organism org2) {
           this.org1 = org1;
           this.org2 = org2;
       }
   
       @Override
       public boolean isOrganism(String context) {
           return org1.isOrganism(context) || org2.isOrganism(context);
       }
   }

   package test.interpreter;
   
   public class AndPeople implements Organism {
       private Organism org1 = null;
       private Organism org2 = null;
   
       public AndPeople(Organism org1, Organism org2) {
           this.org1 = org1;
           this.org2 = org2;
       }
   
       @Override
       public boolean isOrganism(String context) {
           return org1.isOrganism(context) && org2.isOrganism(context);
       }
   }

4. 完成上述步骤，我们就可以开始演示了

   package test.interpreter;
   
   public class InterpreterDemo {
       public static Organism getOrPeople(){
           Organism o1 = new People("people");
           Organism o2 = new People("animal");
           return new OrPeople(o1,o2);
       }
   
       public static Organism getAndPeople(){
           Organism o1 = new People("people");
           Organism o2 = new People("animal");
           return new AndPeople(o1,o2);
       }
   
       public static void main(String[] args) {
           Organism orPeople = getOrPeople();
           Organism andPeople = getAndPeople();
           System.out.println("people or animal is people? "+orPeople.isOrganism("people"));
           System.out.println("people and animal is people? "+andPeople.isOrganism("people"));
       }
   }

   演示结果：

   people or animal is people? true
   people and animal is people? false

说明：

优点： 1、可扩展性比较好，灵活。 2、增加了新的解释表达式的方式。 3、易于实现简单文法。

缺点： 1、可利用场景比较少。 2、对于复杂的文法比较难维护。 3、解释器模式会引起类膨胀。 4、解释器模式采用递归调用方法。