10.7

软件设计                  石家庄铁道大学信息学院

 

实验17：解释器模式（选作）

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解解释器模式的动机，掌握该模式的结构；

2、能够利用解释器模式解决实际问题。

 

[实验任务一]：解释器模式

某机器人控制程序包含一些简单的英文指令，其文法规则如下：

expression ::= direction action distance | composite

composite ::= expression and expression

direction ::= ‘up’ | ‘down’ | ‘left’ | ‘right’

action ::= ‘move’ | ‘run’

distance ::= an integer //一个整数值

如输入：up move 5，则输出“向上移动5个单位”；输入：down run 10 and left move 20，则输出“向下移动10个单位再向左移动20个单位”。

实验要求：

1.     提交类图；

 

 

2. 提交源代码；

// 抽象表达式接口

interface Expression {

    void interpret(Context context);

}

 

 

// 方向解释类

class DirectionExpression implements Expression {

    private String direction;

 

    public DirectionExpression(String direction) {

        this.direction = direction;

    }

 

    @Override

    public void interpret(Context context) {

        context.setDirection(direction);

    }

}

 

 

// 动作解释类

class ActionExpression implements Expression {

    private String action;

 

    public ActionExpression(String action) {

        this.action = action;

    }

 

    @Override

    public void interpret(Context context) {

        context.setAction(action);

    }

}

 

 

// 距离解释类

class DistanceExpression implements Expression {

    private int distance;

 

    public DistanceExpression(int distance) {

        this.distance = distance;

    }

 

    @Override

    public void interpret(Context context) {

        context.setDistance(distance);

    }

}

 

 

import java.util.ArrayList;

import java.util.List;

 

// 复合表达式类

class CompositeExpression implements Expression {

    private List<Expression> expressions = new ArrayList<>();

 

    public void addExpression(Expression expression) {

        expressions.add(expression);

    }

 

    @Override

    public void interpret(Context context) {

        for (Expression expression : expressions) {

            expression.interpret(context);

        }

    }

}

 

 

// 上下文类

class Context {

    private String direction;

    private String action;

    private int distance;

 

    public void setDirection(String direction) {

        this.direction = direction;

    }

 

    public void setAction(String action) {

        this.action = action;

    }

 

    public void setDistance(int distance) {

        this.distance = distance;

    }

 

    public String getInstruction() {

        return direction + " " + action + " " + distance;

    }

}

 

 

 

// 上下文类

class Context {

    private String direction;

    private String action;

    private int distance;

 

    public void setDirection(String direction) {

        this.direction = direction;

    }

 

    public void setAction(String action) {

        this.action = action;

    }

 

    public void setDistance(int distance) {

        this.distance = distance;

    }

 

    public String getInstruction() {

        return direction + " " + action + " " + distance;

    }

}

 

 

 

public class Main {

    public static void main(String[] args) {

        String instruction1 = "up move 5";

        Expression expression1 = InstructionParser.parse(instruction1);

        Context context1 = new Context();

        expression1.interpret(context1);

        System.out.println("指令解析结果：" + context1.getInstruction());

 

        String instruction2 = "down run 10 and left move 20";

        Expression expression2 = InstructionParser.parse(instruction2);

        Context context2 = new Context();

        expression2.interpret(context2);

        System.out.println("指令解析结果：" + context2.getInstruction());

    }

}

3. 注意编程规范。