2024/11/21

软件设计实验十七

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

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";
        }
    }
}

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();
    }
}

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";
        }
    }
}

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;
    }
}

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();
    }
}

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++) {
//如果遇到“and”，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;
    }
}

public class App
{
    public static void main( String[] args )
    {
        String instruction = "down run 10 and left move 20";
        InstructionHandler handler = new InstructionHandler();
        handler.handle(instruction);
        String outString;
        outString = handler.output();
        System.out.println(outString);
    }
}