编译原理词法分析 java简单实现

package com.csray;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class LexicalAnalysis {
	static String id;
	public static void main(String[] args) throws IOException{
		LexicalAnalysis la = new LexicalAnalysis();
		String context = //la.BufferedReaderDemo
							//("C:"+System.getProperty("file.separator")+"Users"+System.getProperty("file.separator")+"Administrator"+System.getProperty("file.separator")+"Desktop"+System.getProperty("file.separator")+"Lexical");
						la.BufferedReaderDemo("C:\Users\Administrator\Desktop\Lexical\lexical.c");
		System.out.println(context);
		
		for(int i = 0; i < context.length();){
			char nowc = context.charAt(i);
			//System.out.println(nowc);
			if(nowc == ' ' || nowc == '
' || nowc == '	'){
				id = "illegalCharacter";
				++i;
			}else if(isAlpha(nowc)){
				i = alphaProcess(context, nowc, i);
			} else if(isDigit(nowc)){
				i = digitProcess(context, nowc, i);
				//i++;
			} else {
				i = otherProcess(context, nowc, i);
				//i++;
			}
		}
	}
	
	//read the lexical.c file to String
	public String BufferedReaderDemo(String path) throws IOException{
		File file = new File(path);
		if(!file.exists() || file.isDirectory())
			throw new FileNotFoundException();
		
		BufferedReader br = new BufferedReader(new FileReader(file));
		String tmp = null;
		StringBuffer sbuff = new StringBuffer();
		tmp = br.readLine();
		while(tmp != null){
			sbuff.append(tmp+" ");
			tmp = br.readLine();
		}
		return sbuff.toString();
	}
	
	//alphaProcess
	public static int alphaProcess(String context, char c, int i){
		StringBuffer word = new StringBuffer();
		while((isAlpha(c)) || (isDigit(c)) || c == '_'){
			word.append(c);
			c = context.charAt(++i);
		}
		//System.out.println(word.toString());
		
		//check this word if or not a keyword
		if(checkKeyword(word.toString())){
			id = "isKeyword";
			System.out.println("( "+ word.toString() + ", " + id +" )");
		} else {
			id = "isCommonWord";
			System.out.println("( "+ word.toString() + ", " + id +" )");
		} 
		
		return i;
	}
	
	// checkKeyword
	public static boolean checkKeyword(String word){
		String keyword = "auto double int struct break else long switch case enum register typedef char "
				+ "extern return union const float short unsigned continue for signed void default goto "
				+ "sizeof volatile do if while static scnaf printf";
		String[] keyWords = keyword.split(" ");
		for(int i = 0; i < keyWords.length; ++i){
			if(word.equals(keyWords[i])){
				return true;
			}
		}
		return false;
	}
	
	// digitProcess
	public static int digitProcess(String context, char c, int i){
		StringBuffer digit = new StringBuffer();
		while(isDigit(c)){
			digit.append(c);
			c = context.charAt(++i);
		}
		id = "isDigit";
		System.out.println("( "+ digit.toString() + ", " + id + " )");
		return i;
	}
	
	// otherProcess
	public static int otherProcess(String context, char c, int i){
		//+ / ( ) { }  += /=  & " "
		StringBuffer operator = new StringBuffer();
		StringBuffer delimiter = new StringBuffer();
		if(c == '+'){
			operator.append(c);
			id = "isOperator";
			c = context.charAt(++i);
			if(c == '='){
				operator.append(c);
				System.out.println("( "+ operator + ", " + id + " )");
				return ++i;
			}else if(c == '+'){
				operator.append(c);
				System.out.println("( "+ operator + ", " + id + " )");
				return ++i;
			}else {
				System.out.println("( "+ operator + ", " + id + " )");
				return --i;
			}
		} else if(c == '('){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		} else if(c == ')'){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		}else if(c == '{'){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		} else if(c == '}'){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		}else if(c == ';'){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		}else if(c == '='){
			operator.append(c);
			id = "isOperator";
			c = context.charAt(++i);
			if(c == '='){
				operator.append(c);
				System.out.println("( "+ operator + ", " + id + " )");
				return ++i;
			}else {
				System.out.println("( "+ operator + ", " + id + " )");
				return i;
			}
		} else if(c == '/'){
			operator.append(c);
			c = context.charAt(++i);
			if(c == '='){
				operator.append(c);
				id = "isOperator";
				System.out.println("( "+ operator + ", " + id + " )");
				return ++i;
			}else if(c == '/'){
				operator.append(c);
				id = "isAnnotation";
				c = context.charAt(++i);
				while(c != ' '){
					operator.append(c);
					c = context.charAt(++i);
				}
				System.out.println("( "+ operator + ", " + id + " )");
				return i;
			}
		}else if(c == '&'){
			operator.append(c);
			id = "isOperator";
			System.out.println("(" + operator + ", " + id + " )");
			return ++i;
		}else if(c == '"'){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		}else if(c == ','){
			delimiter.append(c);
			id = "isDelimiter";
			System.out.println("(" + delimiter + ", " + id + " )");
			return ++i;
		}else if(c == '%'){
			operator.append(c);
			id = "isOperator";
			c = context.charAt(++i);
			if(c == 'd'){
				operator.append(c);
				System.out.println("(" + operator + ", " + id + " )");
				return ++i;
			}
			
			return --i;
		}
		return i;
	}
	
	//isDigit
	public static boolean isDigit(char c){
		if(c >= '0' && c <= '9')
			return true;
		return false;
	}
	
	//isAlpha
	public static boolean isAlpha(char c){
		if(c >= 'A' && c <= 'Z')
			return true;
		else if(c >= 'a' && c <= 'z')
			return true;
		return false;
	}
}

　　实例：

//test
int main()
{
	
	float nu0_m;
	int num = 100;
	num++; 
	scanf("%d", &num);
	printf("%d", num);
	return 0;
}

　　结果：

 //test int main() { 	 	float nu0_m; 	int num = 100; 	num++;  	scanf("%d", &num); 	printf("%d", num); 	return 0; } 
( //test, isAnnotation )
( int, isKeyword )
( main, isCommonWord )
((, isDelimiter )
(), isDelimiter )
({, isDelimiter )
( float, isKeyword )
( nu0_m, isCommonWord )
(;, isDelimiter )
( int, isKeyword )
( num, isCommonWord )
( =, isOperator )
( 100, isDigit )
(;, isDelimiter )
( num, isCommonWord )
( ++, isOperator )
(;, isDelimiter )
( scanf, isCommonWord )
((, isDelimiter )
(", isDelimiter )
(%d, isOperator )
(", isDelimiter )
(,, isDelimiter )
(&, isOperator )
( num, isCommonWord )
(), isDelimiter )
(;, isDelimiter )
( printf, isKeyword )
((, isDelimiter )
(", isDelimiter )
(%d, isOperator )
(", isDelimiter )
(,, isDelimiter )
( num, isCommonWord )
(), isDelimiter )
(;, isDelimiter )
( return, isKeyword )
( 0, isDigit )
(;, isDelimiter )
(}, isDelimiter )