php 解释器模式_解释器模式的概念_解释器模式(2)

{

return i ;

}

}

class Variable extends Expression

{

public int interpret(Context con)

{

//this为调用interpret方法的Variable对象

return con.LookupValue(this);

}

}

//非终结符表达式角色

class Add extends Expression

{

private Expression left ,right ;

public Add(Expression left , Expression right)

{

this.left = left ;

this.right= right ;

}

public int interpret(Context con)

{

return left.interpret(con) + right.interpret(con);

}

}

class Subtract extends Expression

{

private Expression left , right ;

public Subtract(Expression left , Expression right)

{

this.left = left ;

this.right= right ;

}

public int interpret(Context con)

{

return left.interpret(con) - right.interpret(con);

}

}

class Multiply extends Expression

{

private Expression left , right ;

public Multiply(Expression left , Expression right)

{

this.left = left ;

this.right= right ;

}

public int interpret(Context con)

{

return left.interpret(con) * right.interpret(con);

}

}

class Division extends Expression

{

private Expression left , right ;

public Division(Expression left , Expression right)

{

this.left = left ;

this.right= right ;

}

public int interpret(Context con)

{

try{

return left.interpret(con) / right.interpret(con);

}catch(ArithmeticException ae)

{

System.out.println("被除数为0！");

return -11111;

}

}

}

//测试程序，计算 (a*b)/(a-b+2)

public class Test

{

private static Expression ex ;

private static Context con ;

public static void main(String[] args)

{

con = new Context();

//设置变量、常量

Variable a = new Variable();

Variable b = new Variable();

本文来自电脑杂谈，转载请注明本文网址：
http://www.pc-fly.com/a/jisuanjixue/article-29386-2.html