解释器模式 | Interpreter Pattern

解释器模式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。

创建一个表达式接口：

public interface Expression {
public boolean interpret(String context);
}

创建实现上述接口的实体类：

public class TerminalExpression implements Expression {

private String data;

public TerminalExpression(String data){
this.data = data; 
   }

@Override
public boolean interpret(String context) {
if(context.contains(data)){
return true;
      }
return false;
   }
}

public class OrExpression implements Expression {

private Expression expr1 = null;
private Expression expr2 = null;

public OrExpression(Expression expr1, Expression expr2) { 
this.expr1 = expr1;
this.expr2 = expr2;
   }

@Override
public boolean interpret(String context) {       
return expr1.interpret(context) || expr2.interpret(context);
   }
}

public class AndExpression implements Expression {

private Expression expr1 = null;
private Expression expr2 = null;

public AndExpression(Expression expr1, Expression expr2) { 
this.expr1 = expr1;
this.expr2 = expr2;
   }

@Override
public boolean interpret(String context) {       
return expr1.interpret(context) && expr2.interpret(context);
   }
}

使用 Expression 类来创建规则，并解析它们。

public class InterpreterPatternDemo {
//规则：Julie 是一个已婚的女性
public static Expression getMarriedWomanExpression(){
      Expression julie = new TerminalExpression("Julie");
      Expression married = new TerminalExpression("Married");
return new AndExpression(julie, married);     
   }

public static void main(String[] args) {
      Expression isMarriedWoman = getMarriedWomanExpression();

      System.out.println("John is male? " + isMale.interpret("John"));
      System.out.println("Julie is a married women? " 
      + isMarriedWoman.interpret("Married Julie"));
   }
}

输出：

Julie is a married women? true