用JAVA实现的Pascal语言的词法分析器

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<strbuf.length;i++){ //i既是循环变量,也是文件指针
//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<keyWord.length; 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 }。