JAVA编写的 词法分析器.doc

一 实验源码import java.io.FileReader;import java.io.IOException;/* * 此程序0-50为关键字 * 51为标识符 * 52为数字 * 53-61为分隔符 * 62-75为运算符 * 76为字符常量 */public class wordAnalyse static char strbuf = new char500;/定义一个数组,用以存放从文件读取来的字符串 int keywordIndex; /取关键字的类号 /定义50个关键字 String keyWord = abstract, boolean, break, byte, case, catch, char, class, const, continue, default, do, double, else, extends, false, final, finally, float, for, goto, if, implements, import, instanceof, int, interface, long, native, new, null, package, private, protected, public, return, short, static, super, switch, synchronized, this, throw, throws, transient, true, try, void, volatile, while; public static void main(String args) throws IOException wordAnalyse wa = new wordAnalyse();wa.readFile(d:/a.txt);System.out.println(*用JAVA实现的java语言的词法分析器*);System.out.println(*The Result:*+n);wa.run();System.out.println(n+*Complete !*); /从文件中把字符串读取到一个字符数组中private void readFile(String url) throws IOExceptionint ch,i=0;FileReader fr = new FileReader(url);while( (ch=fr.read()!=-1)strbufi+=(char)ch;/判断是否为字母private boolean isLetter(char ch) if(a=ch&ch=z|A=ch&ch=Z)return true;else return false;/判断是否为数字private boolean isDigit(char ch) if(0= ch&ch=9)return true;else return false; /分析整个strbuf里的字符串private void run()StringBuffer buf = new StringBuffer(); /定义一个缓冲区for(int i=0; istrbuf.length;i+)/清除空格 制表符 换行符等字符if(strbufi= |strbufi=t|strbufi=n)i+;if(isLetter(strbufi) int k;buf.delete(0, buf.length();while(isLetter(strbufi)|isDigit(strbufi) buf.append(strbufi); i+;i-; /查找buf里面的字符串是否为关键字for(k =0; k=50)System.out.println(buf + tt +51); if(isDigit(strbufi) buf.delete(0, buf.length(); while(isDigit(strbufi) buf.append(strbufi); i+; i-; System.out.println(buf + tt +52); switch(char)strbufi)case,:System.out.println(strbufi + tt + 53);break;case;:System.out.println(strbufi + tt + 54);break;case(:System.out.println(strbufi + tt + 55);break;case):System.out.println(strbufi + tt + 56);break;case:System.out.println(strbufi + tt + 57);break;case:System.out.println(strbufi + tt + 58);break;case:System.out.println(strbufi + tt + 59);break;case:System.out.println(strbufi + tt + 60);break;case:System.out.println(strbufi + tt + 61);break;case.:System.out.println(strbufi + tt + 62);break;case+:buf.delete(0, buf.length();buf.append(strbufi);i+;if(strbufi=)buf.append(strbufi);System.out.println(buf + tt + 63); elseSystem.out.println(buf + tt + 64); i+;break;case-:buf.delete(0, buf.length();buf.append(strbufi);i+;if(strbufi=)buf.append(strbufi);System.out.println(buf + tt + 65); elseSystem.out.println(buf + tt + 66); i+;break;case*:buf.delete(0, buf.length();buf.append(strbufi);i+;if(strbufi=)buf.append(strbufi);System.out.println(buf + tt + 67); elseSystem.out.println(buf + tt + 68); i+;break;case/:buf.delete(0, buf.length();buf.append(strbufi);i+;if(strbufi=)buf.append(strbufi);System.out.println(buf + tt + 69); elseSystem.out.println(buf + tt + 70); i+;break;case:buf.delete(0, buf.length();buf.append(strbufi);i+;if(strbufi=)buf.append(strbufi);System.out.println(buf + tt + 71); elseSystem.out.println(buf + tt + 72); i+;break;case:buf.delete(0, buf.length();buf.append(strbufi);i+;if(strbufi=)buf.append(strbufi);System.out.println(buf + tt + 73); elseSystem.out.println(buf + tt + 74); i+;break;case:System.out.println(strbufi + tt + 75);i+;if(isLetter(strbufi)|isDi