java代码实现词法分析词法分析器java实现

请用JAVA编程输入一个语句进行词法分析

我最近正在学编译原理，我有c语言实现的词法分析程序，不知可不可以，识别的是TEST语言的单词。

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#includestdio.h

#includectype.h

#includestring.h

#define keywordSum 8

char * keyword[keywordSum] = {"do", "else", "for", "if", "int", "read", "while", "write"};

char singleword[50] = "+-*(){};,:";

char doubleword[10] = "=!|";

char Scanin[300], Scanout[300];

FILE * fin, * fout;

int binaryFind(int low, int high, char * c1, char ** c2) {

int mid;

if(low high) return -1;

mid = (low+high)/2;

if(strcmp(c1, c2[mid]) == 0) return mid;

else if(strcmp(c1, c2[mid]) 0) return binaryFind(mid+1, high, c1, c2);

else return binaryFind(low, mid-1, c1, c2);

}

int TESTscan() {

char ch, token[40];

int es = 0, j, n;

printf("请输入源文件名(包括路径):");

scanf("%s", Scanin);

printf("请输入词法分析输出文件名(包括路径):");

scanf("%s", Scanout);

if((fin=fopen(Scanin, "r")) == NULL) {

printf("\n打开词法分析输入文件出错!\n");

return 1;

}

if((fout=fopen(Scanout, "w")) == NULL) {

printf("\n创建词法分析输出文件出错!\n");

return 2;

}

// printf("%c", getc(fin));

ch = getc(fin);

while(ch != EOF) {

while(ch==' ' || ch=='\n' || ch=='\t') {

ch = getc(fin);

}

if(isalpha(ch)) { //标识符

token[0] = ch;

j = 1;

ch = getc(fin);

while(isalnum(ch)) { //判断当前字符是否是字母或数字

token[j++] = ch;

ch = getc(fin);

}

token[j] = '\0';

// printf("%s", token);

n = binaryFind(0, keywordSum-1, token, keyword);

if(n 0 ) {

fprintf(fout, "%s\t%s\n", "ID", token);

} else {

fprintf(fout, "%s\t%s\n", token, token);

}

} else if(isdigit(ch)) { //数字

token[0] = ch;

j = 1;

ch = getc(fin);

while(isdigit(ch)) {

token[j++] = ch;

ch = getc(fin);

}

token[j] = '\0';

fprintf(fout, "%s\t%s\n", "NUM", token);

} else if(strchr(singleword, ch) 0) { //singleword

token[0] = ch;

token[1] = '\0';

ch = getc(fin);

fprintf(fout, "%s\t%s\n", token, token);

} else if(strchr(doubleword, ch) 0) { //doubleword

token[0] = ch;

ch = getc(fin);

if(ch=='=' (token[0]==''||token[0]=='' || token[0] == '!')) {

token[1] = ch;

token[2] = '\0';

ch = getc(fin);

} else if((ch=='')||(ch=='|')||(ch=='=') ch==token[0]) {

token[1] = ch;

token[2] = '\0';

ch = getc(fin);

} else {

token[1] = '\0';

}

fprintf(fout, "%s\t%s\n", token, token);

} else if(ch == '/') { //注释

ch = getc(fin);

if(ch == '*') {

char ch1;

ch1 = getc(fin);

do {

ch = ch1;

ch1 = getc(fin);

} while((ch!='*'||ch1!='/') ch1!=EOF);

ch = getc(fin);

} else {

token[0] = '/';

token[1] = '\0';

fprintf(fout, "%s\t%s\n", token, token);

}

} else {

token[0] = ch;

token[1] = '\0';

ch = getc(fin);

es = 3;

fprintf(fout, "%s\t%s\n", "ERROR", token);

}

fclose(fin);

fclose(fout);

return es;

}

void main() {

int es = 0;

es = TESTscan();

if(es 0) {

printf("词法分析有错, 编译停止!\n");

} else {

printf("词法分析成功!\n");

}

如何用JAVA编写词法分析器程序

我也做过这个作业

package source;

import java.util.LinkedList;

public class LexicalAnalysis

{

//私有变量声明

private LinkedListWord optr = new LinkedListWord();

private String exp;

//词法分析

public LinkedListWord lexical_analysis(String exp)

{

char ch = '\0'; //当前文件指针内容

int index = 0; //文件指针

StringBuffer strToken = new StringBuffer("");

//扫描处理字符串

while(true)

{

ch = exp.charAt(index);

index++;

//标识符(字母开头，数字或字符组成)

if(Character.isLetter(ch))

{

while(Character.isLetter(ch) || Character.isDigit(ch))

{

strToken.append(ch);

ch = exp.charAt(index);

index++;

}

index--;

String str = strToken.toString();

if(str.equals("if"))

optr.add(new Word(str, 13));

else if(str.equals("else"))

optr.add(new Word(str, 14));

else if(str.equals("then"))

optr.add(new Word(str, 15));

else

optr.add(new Word(str, 26));

}

//数字

else if(Character.isDigit(ch))

{

while(Character.isDigit(ch))

{

strToken.append(ch);

ch = exp.charAt(index);

index++;

}

index--;

optr.add(new Word(strToken.toString(), 26));

}

//加号或自加

else if(ch == '+')

{

ch = exp.charAt(index);

index++;

if(ch == '+')

optr.add(new Word("++", 21));

else if(ch == '=')

optr.add(new Word("+=", 16));

else

{

index--;

optr.add(new Word("+", 19));

}

//加号或自加

else if(ch == '-')

{

ch = exp.charAt(index);

index++;

if(ch == '-')

optr.add(new Word("--", 21));

else if(ch == '=')

optr.add(new Word("-=", 16));

else

{

index--;

optr.add(new Word("-", 19));

}

//乘法或乘幂

else if(ch == '*')

{

ch = exp.charAt(index);

index++;

if(ch == '*')

optr.add(new Word("**", 20));

else if(ch == '=')

optr.add(new Word("*=", 16));

else

{

index--;

optr.add(new Word("*", 20));

}

//除法或注释

else if(ch == '/')

{

ch = exp.charAt(index);

index++;

//多行注释

if(ch == '*')

{

while(true)

{

ch = exp.charAt(index);

index++;

if(ch == '*')

{

ch = exp.charAt(index);

index++;

if(ch == '/') break;

else if(ch == '\n')

{

exp = Input.newLine();

index = 0;

ch = exp.charAt(index);

index++;

}

else index--;

}

else if(ch == '#')

{

int tIndex = index - 1;

if(exp.length() tIndex+9)

{

String end = exp.substring(tIndex, tIndex+9);

if(end.equals("#?e_N_d?#")) break;

}

else

{

System.out.println("非法符号\'#\'后的语句忽略！");

exp = Input.newLine();

index = 0;

break;

}

else if(ch == '\n')

{

exp = Input.newLine();

index = 0;

}

//单行注释

else if(ch == '/')

break;

else if(ch == '=')

optr.add(new Word("/=", 16));

else

{

index--;

optr.add(new Word("/", 20));

}

//大于或大于等于或右移

else if(ch == '')

{

ch = exp.charAt(index);

index++;

if(ch == '=')

optr.add(new Word("=", 18));

else if(ch == '')

optr.add(new Word("", 20));

else

{

index--;

optr.add(new Word("", 18));

}

//小于或小于等于或左移

else if(ch == '')

{

ch = exp.charAt(index);

index++;

if(ch == '=')

optr.add(new Word("=", 18));

else if(ch == '')

optr.add(new Word("", 20));

else

{

index--;

optr.add(new Word("", 18));

}

//赋值或等于

else if(ch == '=')

{

ch = exp.charAt(index);

index++;

if(ch == '=')

optr.add(new Word("==", 18));

else

{

index--;

optr.add(new Word("=", 16));

}

//或运算按位或

else if(ch == '|')

{

ch = exp.charAt(index);

index++;

if(ch == '|')

optr.add(new Word("||", 17));

else

{

index--;

optr.add(new Word("|", 20));

}

//与运算

else if(ch == '')

{

ch = exp.charAt(index);

index++;

if(ch == '')

optr.add(new Word("", 17));

else

{

index--;

optr.add(new Word("", 20));

}

//非运算或不等于

else if(ch == '!')

{

ch = exp.charAt(index);

index++;

if(ch == '=')

optr.add(new Word("!=", 18));

else

{

index--;

optr.add(new Word("!", 21));

}

//按位亦或

else if(ch == '^')

optr.add(new Word("^", 20));

//取模运算

else if(ch == '%')

optr.add(new Word("%", 20));

//左括号

else if(ch == '(')

optr.add(new Word("(", 22));

//右括号

else if(ch == ')')

optr.add(new Word(")", 23));

//左大括号

else if(ch == '{')

optr.add(new Word("{", 24));

//右大括号

else if(ch == '}')

optr.add(new Word("}", 25));

//结束扫描标志为：#?e_N_d?#

else if(ch == '\n')

{

break;

}

else if(ch == '#')

{

int tIndex = index - 1;

if(exp.length() tIndex+9)

{

String end = exp.substring(tIndex, tIndex+9);

if(end.equals("#?e_N_d?#"))

{

optr.add(new Word("#", 27));

break;

}

else

{

System.out.println("非法符号\'#\'后的语句忽略！");

optr.add(new Word("#", 27));

break;

}

//清空扫描串

strToken.setLength(0);

}

return optr;

}

java 词法分析思路

java 有 System.in()获取标准键盘输入

你可以用一个 StringBuffer 来装这些输入例如

StringBuffer sb=System.in();

即可获取你输入的字符串~~

想获取每个字符的话可以如下

byte [] buf=sb.getBytes();

for(int i=0;ibuf.size();i++){

System.out.println(buf[i]);

}

怎么用java写一个词法分析器

首先看下我们要分析的代码段如下：

输出结果如下：

输出结果(a).PNG

输出结果(b).PNG

输出结果(c).PNG

括号里是一个二元式：（单词类别编码，单词位置编号）

代码如下：

1234567891011121314

package Yue.LexicalAnalyzer; import java.io.*; /* * 主程序 */public class Main { public static void main(String[] args) throws IOException { Lexer lexer = new Lexer(); lexer.printToken(); lexer.printSymbolsTable(); }}

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283

package Yue.LexicalAnalyzer; import java.io.*;import java.util.*; /* * 词法分析并输出 */public class Lexer { /*记录行号*/ public static int line = 1; /*存放最新读入的字符*/ char character = ' '; /*保留字*/ HashtableString, KeyWord keywords = new HashtableString, KeyWord(); /*token序列*/ private ArrayListToken tokens = new ArrayListToken(); /*符号表*/ private ArrayListSymbol symtable = new ArrayListSymbol(); /*读取文件变量*/ BufferedReader reader = null; /*保存当前是否读取到了文件的结尾*/ private Boolean isEnd = false; /* 是否读取到文件的结尾 */ public Boolean getReaderState() { return this.isEnd; } /*打印tokens序列*/ public void printToken() throws IOException { FileWriter writer = new FileWriter("E:\\lex.txt"); System.out.println("词法分析结果如下："); System.out.print("杜悦-2015220201031\r\n\n"); writer.write("杜悦-2015220201031\r\n\r\n"); while (getReaderState() == false) { Token tok = scan(); String str = "line " + tok.line + "\t(" + tok.tag + "," + tok.pos + ")\t\t" + tok.name + ": " + tok.toString() + "\r\n"; writer.write(str); System.out.print(str); } writer.flush(); } /*打印符号表*/ public void printSymbolsTable() throws IOException { FileWriter writer = new FileWriter("E:\\symtab1.txt"); System.out.print("\r\n\r\n符号表\r\n"); System.out.print("编号\t行号\t名称\r\n"); writer.write("符号表\r\n"); writer.write("编号 " + "\t行号 " + "\t名称 \r\n"); IteratorSymbol e = symtable.iterator(); while (e.hasNext()) { Symbol symbol = e.next(); String desc = symbol.pos + "\t" + symbol.line + "\t" + symbol.toString(); System.out.print(desc + "\r\n"); writer.write(desc + "\r\n"); } writer.flush(); } /*打印错误*/ public void printError(Token tok) throws IOException{ FileWriter writer = new FileWriter("E:\\error.txt"); System.out.print("\r\n\r\n错误词法如下：\r\n"); writer.write("错误词法如下：\r\n"); String str = "line " + tok.line + "\t(" + tok.tag + "," + tok.pos + ")\t\t" + tok.name + ": " + tok.toString() + "\r\n"; writer.write(str); } /*添加保留字*/ void reserve(KeyWord w) { keywords.put(w.lexme, w); } public Lexer() { /*初始化读取文件变量*/ try { reader = new BufferedReader(new FileReader("E:\\输入.txt")); } catch (IOException e) { System.out.print(e); } /*添加保留字*/ this.reserve(KeyWord.begin); this.reserve(KeyWord.end); this.reserve(KeyWord.integer); this.reserve(KeyWord.function); this.reserve(KeyWord.read); this.reserve(KeyWord.write); this.reserve(KeyWord.aIf); this.reserve(KeyWord.aThen); this.reserve(KeyWord.aElse); } /*按字符读*/ public void readch() throws IOException { character = (char) reader.read(); if ((int) character == 0xffff) { this.isEnd = true; } } /*判断是否匹配*/ public Boolean readch(char ch) throws IOException { readch(); if (this.character != ch) { return false; } this.character = ' '; return true; } /*数字的识别*/ public Boolean isDigit() throws IOException { if (Character.isDigit(character)) { int value = 0; while (Character.isDigit(character)) { value = 10 * value + Character.digit(character, 10); readch(); } Num n = new Num(value); n.line = line; tokens.add(n); return true; } else return false; } /*保留字、标识符的识别*/ public Boolean isLetter() throws IOException { if (Character.isLetter(character)) { StringBuffer sb = new StringBuffer(); /*首先得到整个的一个分割*/ while (Character.isLetterOrDigit(character)) { sb.append(character); readch(); } /*判断是保留字还是标识符*/ String s = sb.toString(); KeyWord w = keywords.get(s); /*如果是保留字的话，w不应该是空的*/ if (w != null) { w.line = line; tokens.add(w); } else { /*否则就是标识符，此处多出记录标识符编号的语句*/ Symbol sy = new Symbol(s); Symbol mark = sy; //用于标记已存在标识符 Boolean isRepeat = false; sy.line = line; for (Symbol i : symtable) { if (sy.toString().equals(i.toString())) { mark = i; isRepeat = true; } } if (!isRepeat) { sy.pos = symtable.size() + 1; symtable.add(sy); } else if (isRepeat) { sy.pos = mark.pos; } tokens.add(sy); } return true; } else return false; } /*符号的识别*/ public Boolean isSign() throws IOException { switch (character) { case '#': readch(); AllEnd.allEnd.line = line; tokens.add(AllEnd.allEnd); return true; case '\r': if (readch('\n')) { readch(); LineEnd.lineEnd.line = line; tokens.add(LineEnd.lineEnd); line++; return true; } case '(': readch(); Delimiter.lpar.line = line; tokens.add(Delimiter.lpar); return true; case ')': readch(); Delimiter.rpar.line = line; tokens.add(Delimiter.rpar); return true; case ';': readch(); Delimiter.sem.line = line; tokens.add(Delimiter.sem); return true; case '+': readch(); CalcWord.add.line = line; tokens.add(CalcWord.add); return true; case '-': readch(); CalcWord.sub.line = line; tokens.add(CalcWord.sub); return true; case '*': readch(); CalcWord.mul.line = line; tokens.add(CalcWord.mul); return true; case '/': readch(); CalcWord.div.line = line; tokens.add(CalcWord.div); return true; case ':': if (readch('=')) { readch(); CalcWord.assign.line = line; tokens.add(CalcWord.assign); return true; } break; case '': if (readch('=')) { readch(); CalcWord.ge.line = line; tokens.add(CalcWord.ge); return true; } break; case '': if (readch('=')) { readch(); CalcWord.le.line = line; tokens.add(CalcWord.le); return true; } break; case '!': if (readch('=')) { readch(); CalcWord.ne.line = line; tokens.add(CalcWord.ne); return true; } break; } return false; } /*下面开始分割关键字，标识符等信息*/ public Token scan() throws IOException { Token tok; while (character == ' ') readch(); if (isDigit() || isSign() || isLetter()) { tok = tokens.get(tokens.size() - 1); } else { tok = new Token(character); printError(tok); } return tok; }}

文章题目：java代码实现词法分析词法分析器java实现
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