无涯教程-Java 解释器模式解释器这个名词想必大家都不会陌生，比如编译原理中，一个算术表达式通过词法分析器形成词法单元

解释器这个名词想必大家都不会陌生，比如编译原理中，一个算术表达式通过词法分析器形成词法单元，而后这些词法单元再通过语法分析器构建语法分析树，最终形成一颗抽象的语法分析树。诸如此类的例子也有很多，比如编译器、正则表达式等等,这种模式属于行为模式。

解释器模式实例

无涯教程将创建一个 Expression 接口和实现 Expression 接口的具体类。定义了一个 TerminalExpression 类，该类充当所讨论上下文的主要解释器。其他类 OrExpression ， AndExpression 用于创建组合表达式。

演示类 InterpreterPatternDemo 将使用 Expression 类创建规则并演示表达式的解析。

第1步 - 创建一个表达式接口。

Expression.java

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

第2步 - 创建实现上述接口的具体类。

TerminalExpression.java

public class TerminalExpression implements Expression {
private String data;
public TerminalExpression(String data){
this.data = data;
}
@Override
public boolean interpret(String context) {
  </span><span class="kwd">if</span><span class="pun">(</span><span class="pln">context</span><span class="pun">.</span><span class="pln">contains</span><span class="pun">(</span><span class="pln">data</span><span class="pun">)){</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">true</span><span class="pun">;</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
  </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">false</span><span class="pun">;</span><span class="pln">

}
}

OrExpression.java

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);
}
}

AndExpression.java

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);
}
}

第3步 - InterpreterPatternDemo 使用 Expression 类创建规则，然后解析它们。

InterpreterPatternDemo.java

public class InterpreterPatternDemo {
//Rule: Robert and John are male
public static Expression getMaleExpression(){
Expression robert = new TerminalExpression("Robert");
Expression john = new TerminalExpression("John");
return new OrExpression(robert, john);
}
//Rule: Julie is a married women
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 isMale = getMaleExpression();
Expression isMarriedWoman = getMarriedWomanExpression();
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"John is male? "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> isMale</span><span class="pun">.</span><span class="pln">interpret</span><span class="pun">(</span><span class="str">"John"</span><span class="pun">));</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"Julie is a married women? "</span><span class="pln"> </span><span class="pun">+</span><span class="pln"> isMarriedWoman</span><span class="pun">.</span><span class="pln">interpret</span><span class="pun">(</span><span class="str">"Married Julie"</span><span class="pun">));</span><span class="pln">

}
}

第4步 - 验证输出。

John is male? true
Julie is a married women? true

无涯教程-Java 解释器模式

解释器模式实例

参考链接