用JAVA实现的Pascal语言的词法分析器
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
import java.io.*;
public class WordAnalyse {
static char[] strbuf = new char[150];//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
String[] keyWord = {"and","begin","const","div","do","else","end",
"function","if","integer","not","or","procedure","program",
"read","real","then","type","var","while","write"};
public static void main(String[] args) throws IOException {
WordAnalyse wa = new WordAnalyse();
wa.readFile("d:/pascal.txt");
System.out.println("******用JAVA实现的Pascal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 IOException{
int ch,i=0;
FileReader fr = new FileReader(url);
while( (ch=fr.read())!=-1){
strbuf[i++]=(char)ch;
}
}
private boolean isLetter(char ch) {
if('a'<=ch&ch<='z'||'A'<=ch&ch<='Z')
return true;
else return false;
}
private boolean isDigit(char ch) {
if('0'<= ch&&ch<='9')
return true;
else return false;
}
private void run(){ //分析整个strbuf里的字符串
StringBuffer buf = new StringBuffer(); //定义一个缓冲区
for(int i=0; i //当读头读到space\enter\line的时候,忽略! if(strbuf[i]==' '||strbuf[i]=='\t'||strbuf[i]=='\n') i++; if(isLetter(strbuf[i])) { int k; buf.delete(0, buf.length()); while(isLetter(strbuf[i])||isDigit(strbuf[i])) { buf.append(strbuf[i]); i++; } i--; //查找buf里面的字符串是否为关键字 for(k =0; k if(new String(buf).equals(keyWord[k])){ keywordIndex = k; System.out.println(buf + "\t\t" +keywordIndex); break; } } if(k>20) System.out.println(buf + "\t\t" +21); } if(isDigit(strbuf[i])) { 1 buf.delete(0, buf.length()); while(isDigit(strbuf[i])){ buf.append(strbuf[i]); i++; } i--; System.out.println(buf + "\t\t" +22); } switch((char)strbuf[i]){ case',':System.out.println(strbuf[i] + "\t\t" + 23);break; case';':System.out.println(strbuf[i] + "\t\t" + 24);break; case'.':System.out.println(strbuf[i] + "\t\t" + 26);break; case'(':System.out.println(strbuf[i] + "\t\t" + 27);break; case')':System.out.println(strbuf[i] + "\t\t" + 28);break; case'[':System.out.println(strbuf[i] + "\t\t" + 29);break; case']':System.out.println(strbuf[i] + "\t\t" + 30);break; case'+':System.out.println(strbuf[i] + "\t\t" + 34);break; case'-':System.out.println(strbuf[i] + "\t\t" + 35);break; case'=':System.out.println(strbuf[i] + "\t\t" + 38);break; case':':{ buf.delete(0, buf.length()); buf.append(strbuf[i]); i++; if(strbuf[i]=='='){ buf.append(strbuf[i]); System.out.println(buf + "\t\t" + 44); } else{ System.out.println(buf + "\t\t" + 25); i++; } };break; case'>':{ buf.delete(0, buf.length()); buf.append(strbuf[i]); i++; if(strbuf[i]=='='){ buf.append(strbuf[i]); System.out.println(buf + "\t\t" + 43); } else{ System.out.println(buf + "\t\t" + 40); i--; } };break; case'<':{ buf.delete(0, buf.length()); buf.append(strbuf[i]); i++; if(strbuf[i]=='='){ buf.append(strbuf[i]); System.out.println(buf + "\t\t" + 42); i++; } else if(strbuf[i]=='>'){ buf.append(strbuf[i]); System.out.println(buf + "\t\t" + 41); i++; } else{ System.out.println(buf + "\t\t" + 39); i++; } };break; }//switch结束 } } 2 }