compiler.java

词法分析器的JAVA实现

package byy;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Compiler {
 
	static String keyword[] = {"AND","BEGIN","CONST","DIV","DO","ELSE","END",
		       "FUNCTION","IF","INTEGER","NOT","OR","PROCEDURE",
		       "PROGRAM","READ","REAL","THEN","TYPE","VAR","WHILE",
		       "WRITE"};
	static String symbol[] = {",",";",":",".","(",")","[","]","..","+=","-=",
				"+","-","*","/","=","<",">","<>","<=",">=",":=","{","}","#"};
	
	public static boolean isNumeric(String str){
		  for (int i = str.length();--i>=0;){   
		   if (!Character.isDigit(str.charAt(i))){
		    return false;
		   }
		  }
		  return true;
		 }
	
	public static int match(String str){
		for(int i = 0;i < keyword.length;i++){
			if(str.equalsIgnoreCase(keyword[i]))
				return i;
		}
		for(int i = 0;i < symbol.length;i++){
			if(str.equals(symbol[i]))
				return i + 23;
		}
		if(isNumeric(str))
			return 22;
		else
			return 21;
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		StringBuffer buf = new StringBuffer();
		File f = new File("c:\\pascal.txt");
		if(f.exists()){
			try {
				FileReader fr = new FileReader("c:\\pascal.txt");
				BufferedReader br = new BufferedReader(fr);
				String temp = null;
				Pattern pt = 
					Pattern.compile("((_|[a-zA-Z])(\\p{Alnum})*)|\\+=|-=|:=|-|\\+|>=|<=|<>|<|>|=|:|;|\\(|\\)|\\{|\\}|\\[|\\]|,|#|\\*|/|\\..|\\.|\\d{1,50}");
				System.out.println("The Result :");
				while((temp = br.readLine()) != null){
					Matcher ma = pt.matcher(temp);
					while(ma.find()){
						System.out.println("	" + ma.group(0) + "	,	" + match(ma.group()));
						ma.appendReplacement(buf," ");
					}
					ma.appendTail(buf);
				}
				System.out.println("   OVER !");
		//		System.out.println(buf);
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}