语法分析器（二） 识别多错误 Java版

想了解更多内容，移步至编译原理专栏

==========================2021.12.22 更新===================================

整理了一下代码，同步到了gitee

https://gitee.com/godelgnis/lrparserhttps://gitee.com/godelgnis/lrparser

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 在上次实验的基础上进行改进，能够识别多个错误，本文的只进行了部分数据的测试，所以可能会有其他错误识别不出来

部分缺失的代码请参考我之前写的博客，可以查看完整的代码

本博客的程序只能识别赋值语句，能够输出并输出多种错误的类型，并且实现了错误定位功能

package codescanner;

import java.util.ArrayList;

public class IrParser {

	private Analyzer analyzer;
	private ArrayList<Word> list = new ArrayList<>();
	private Word word;
	private int index = 0; // 从列表中获取单词的下标
	private boolean error = false;	//标记是否检测到错误
	public int rowNum = 1;		//用来记录行数

	public IrParser() {
		analyzer = new Analyzer("input.txt", "output.txt");
		analyzer.analyze(analyzer.getContent());
		list = analyzer.getList();
	}

	public void parse() {
		if(list.size() > 0 && (word = getNext(list)).getTypenum() !=1) {
			error = true;
			index--;
			System.out.print("begin错误");
			System.out.println(" 识别符号为 " + word.getWord() + " " +  "位置: " + rowNum + "行");
		}
		//分隔符
		pretreatment();
		if(list.size() > 0) {
			word = getNext(list);
			if (word == null) {
				error = true;
				System.out.print("缺end错误");
				System.out.println(" 文件已结束 " +  "位置: " + rowNum + "行");
			}else if(word.getTypenum() != 6){
				error = true;
				System.out.print("缺end错误");
				System.out.println(" 识别符号为 " + word.getWord() + " " +  "位置: " + rowNum + "行");
			}
		}
		if (!error) {
			System.out.println("success");
		}
	}
	/**
	 * 预处理
	 */
	public void pretreatment() {
		while (word != null && word.getTypenum() != 6) {
			statement();
		}
		index--;
	}
	/**
	 * 赋值错误和语句错误
	 */
	public void statement() {
		word = getNext(list);
		if (word != null && word.getTypenum() != 26) {
			if (word.getTypenum() == 10) {
				assignment();
			} else {
				if (word.getTypenum() != 0 && word.getTypenum() != 6) {
					
					error = true;
					System.out.print("语句错误");
					System.out.println(" 识别符号为 " + word.getWord() + " " +  "位置: " + rowNum + "行");
					assignment();
				}
			}
		}
	}
	/**
	 * 赋值号错误
	 */
	public void assignment() {
		word = getNext(list);
		if (word != null ) {
			if (word.getTypenum() == 18) {
				expression();
			} else {
				error = true;
				System.out.print("赋值号错误");
				System.out.println(" 识别符号为 " + word.getWord() + " " +  "位置: " + + rowNum + "行");
				expression();
			}
		}
	}
	
	/**
	 * 分析表达式表达式
	 */
	public void expression() {
		if (word.getTypenum() == 26) 
			return;
		word = getNext(list);
		if (word != null) {
			term();
			while (word.getTypenum() == 13 || word.getTypenum() == 14) {
				word = getNext(list);
				term();
			}
		}
	}
	public void term() {
		if (word != null) {
			factor();
			while (word.getTypenum() == 15 || word.getTypenum() == 16) {
				
				word = getNext(list);
				factor();
			}
		}
	}
	/**
	 * "("错误 和 表达式错误
	 */ 
	public void factor() {
		if (word != null) {
			
			if (word.getTypenum() == 10 || word.getTypenum() == 11) {
				word = getNext(list);
			} else if (word.getTypenum() == 27) {
				expression();
				if (word.getTypenum() == 28) {
					
					word = getNext(list);
				} else {
					error = true;
					System.out.print("')'错误");
					System.out.println(" 识别符号为 " + word.getWord() + " " +  "位置: " + rowNum + "行");
					if (word.getTypenum() == 26) 
						return;
					word = getNext(list);
				}
			} else {
				error = true;
				System.out.print("表达式错误");
				System.out.println(" 识别符号为 " + word.getWord() + " " +  "位置: " + rowNum + "行");
				if (word.getTypenum() == 26) 
					return;
				word = getNext(list);
			}
			
		}
	}
	/**
	 * 取下一个词，如果是读取到换行，就增加行数，
	 * @param list
	 * @return
	 */
	public Word getNext(ArrayList<Word> list) {
		if (index < list.size()) {
			Word currentWord = list.get(index++);
			while (currentWord.getTypenum() == 30 || currentWord.getTypenum() == 31) {
				//因为一个换行字符被我转换成长度为2字符串了，所以要除以2
				rowNum += currentWord.getWord().length()/2;
				currentWord = list.get(index++);
			}
			return currentWord;
		} else {
			return null;
		}
	}

	public int getIndex() {
		return index;
	}

	public void setIndex(int index) {
		this.index = index;
	}

	public static void main(String[] args) {
		IrParser parser = new IrParser();
		parser.parse();
	}
}

实验数据 

//正确测试例子
//begin a:=9; x:=2*3; b:=a+x end #

//缺begin错误
 x:=a+b*c;  

//表达式错误
a:=2+; x:=2*3; b:=a+x; 

//赋值符号错误
a=9; x:=2*3; b:=a+x;

//')'错误 和 表达式错误
a:=9; x:=2*3; b:=(a+;

//语句错误
//if a>0 then a:=1;
if :=1;
//表达式错误
x:=4+;

//缺end错误
x:=a+b*c; 
#

以上的数据应该在当前项目目录下新建一个文件“input.txt”， 并且以“#”作为文件结束符