《软件设计》解释器模式

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；

3. 注意编程规范。

1、类图

2、源代码

AbstractNode.java

package org.example;

public abstract class AbstractNode {
public abstract String interpret();
}

ActionNode.java

package org.example;

public class ActionNode extends AbstractNode{
    private String action;

    public ActionNode(String action) {
        this.action = action;
    }

    //动作（移动方式）表达式的解释操作
    public String interpret() {
        if (action.equalsIgnoreCase("move")) {
            return "移动";
        }
        else if (action.equalsIgnoreCase("run")) {
            return "快速移动";
        }
        else {
            return "无效指令";
        }
    }
}

AndNode.java

package org.example;

public class AndNode extends AbstractNode{
    private AbstractNode left; //And的左表达式
    private AbstractNode right; //And的右表达式

    public AndNode(AbstractNode left, AbstractNode right) {
        this.left = left;
        this.right = right;
    }

    //And表达式解释操作
    public String interpret() {
        return left.interpret() + "再" + right.interpret();
    }
}

DirectionNode.java

package org.example;

public class DirectionNode extends AbstractNode{
    private String direction;

    public DirectionNode(String direction) {
        this.direction = direction;
    }

    //方向表达式的解释操作
    public String interpret() {
        if (direction.equalsIgnoreCase("up")) {
            return "向上";
        }
        else if (direction.equalsIgnoreCase("down")) {
            return "向下";
        }
        else if (direction.equalsIgnoreCase("left")) {
            return "向左";
        }
        else if (direction.equalsIgnoreCase("right")) {
            return "向右";
        }
        else {
            return "无效指令";
        }
    }
}

DistanceNode.java

package org.example;

public class DistanceNode extends AbstractNode{
    private String distance;

    public DistanceNode(String distance) {
        this.distance = distance;
    }

    //距离表达式的解释操作
    public String interpret() {
        return this.distance;
    }
}

InstructionHandler.java

package org.example;

import java.util.Stack;

public class InstructionHandler {
    private String instruction;
    private AbstractNode node;
    public void handle(String instruction) {
        AbstractNode left = null, right = null;
        AbstractNode direction = null, action = null, distance = null;
        Stack stack = new Stack(); //声明一个栈对象用于存储抽象语法树
        String[] words = instruction.split(" "); //以空格分隔指令字符串
        for (int i = 0; i < words.length; i++) {
            //本实例采用栈的方式来处理指令，如果遇到“and”，则将其后的三个单词作为三个终结符表达式连成一个简单句子SentenceNode作为“and”的右表达式，而将从栈顶弹出的表达式作为“and”的左表达式，最后将新的“and”表达式压入栈中。
            if (words[i].equalsIgnoreCase("and")) {
                left = (AbstractNode)stack.pop(); //弹出栈顶表达式作为左表达式
                String word1= words[++i];
                direction = new DirectionNode(word1);
                String word2 = words[++i];
                action = new ActionNode(word2);
                String word3 = words[++i];
                distance = new DistanceNode(word3);
                right = new SentenceNode(direction,action,distance); //右表达式
                stack.push(new AndNode(left,right)); //将新表达式压入栈中
            }
            //如果是从头开始进行解释，则将前三个单词组成一个简单句子SentenceNode并将该句子压入栈中
            else {
                String word1 = words[i];
                direction = new DirectionNode(word1);
                String word2 = words[++i];
                action = new ActionNode(word2);
                String word3 = words[++i];
                distance = new DistanceNode(word3);
                left = new SentenceNode(direction,action,distance);
                stack.push(left); //将新表达式压入栈中
            }
        }
        this.node = (AbstractNode)stack.pop(); //将全部表达式从栈中弹出
    }

    public String output() {
        String result = node.interpret(); //解释表达式
        return result;
    }
}

SentenceNode.java

package org.example;

public class SentenceNode extends AbstractNode {
    private AbstractNode direction;
    private AbstractNode action;
    private AbstractNode distance;

    public SentenceNode(AbstractNode direction, AbstractNode action, AbstractNode distance) {
        this.direction = direction;
        this.action = action;
        this.distance = distance;
    }

    //简单句子的解释操作
    public String interpret() {
        return direction.interpret() + action.interpret() + distance.interpret();
    }
}

Main.java

package org.example;

import java.util.*;

public class Main {

    public static void main(String[] args) {
        boolean a = true;
        // TODO Auto-generated method stub
      /* String instruction1 = "up move 5 and down run 10 and left move 5";
        String instruction2 = "down run 10 and left move 20";*/
        Scanner scanner = new Scanner(System.in);
        System.out.println("是否要控制机器人移动？(yes/no)");
        String input = scanner.nextLine();
        if (input.equals("yes") || input.equals("Yes") || input.equals("y") || input.equals("Y")) {
            System.out.println("请输入命令: ");
            String instruction1 = scanner.nextLine();
            InstructionHandler handler = new InstructionHandler();
            handler.handle(instruction1);
            String outString;
            outString = handler.output();
            System.out.println(outString);
            while (true) {
                System.out.println("是否要继续输入命令？(yes/no)");
                String input2 = scanner.nextLine();
                if (input2.equals("yes") || input2.equals("Yes") || input2.equals("y") || input2.equals("Y")) {
                    System.out.println("请输入命令: ");
                    String instruction2 = scanner.nextLine();
                    handler.handle(instruction2);
                    outString = handler.output();
                    System.out.println(outString);
                } else {
                    System.out.println("结束程序");
                    break;
                }
            }
       } else {
            System.out.println("结束程序");
        }
    }
}