词法分析(Java实现)不用状态机

老师要求不能用自动机等知识,就是想让我们凑代码,体验下不用自动机的痛苦

package analyse;import java.io.*;import java.util.*;public class Analyse {FileReader fileReader = null;BufferedReader reader = null;StringBuffer token = null;//缓冲区,缓冲临时未完全tokenchar nowChar;//当前字符public char getNowChar() {return nowChar;}public void setNowChar(char nowChar) {this.nowChar = nowChar;}boolean isEnd = false;//判断是否到达文件尾public static String keyWorkStr[] = {"abstract","assert","boolean","break","byte","case","catch","char","const","class","continue","default","do","double","else","enum","extends","final","finally","float","for","goto","if","implements","import","instanceof","int","interface","long","native","new","package","private","protected","public","return","short","static","strictfp","super","switch","synchronized","this","throw","throws","transient","try","void","volatile","while","true","false"};//关键字字符串public static String operaStr[] = {"+","-","*","/","++","--","<<",">>","<",">",">=","<=","==","=","*=","+=","-=","/=","%=","&=","|=","^=","&","&&","||","!=","~","<<=",">>=","%"};//操作符字串public static String specialStr[] = {"(",")","[","]","!",":",".",",","{","}","#",";","@","?"};//特殊符号字串public static Set<String> keyWork = new HashSet<String>(Arrays.asList(keyWorkStr));//关键字集合public static Set<String> special = new HashSet<String>(Arrays.asList(specialStr));//特殊符号集合public static Set<String> opera = new HashSet<String>(Arrays.asList(operaStr));//操作符集合/** * 入口函数 */public static void main(String[] args) {Analyse an = new Analyse();an.start();}/** * 启动分析 */public void start(){step0(nextChar());}/** * 读取下一个字符,并且更新当前字符 * 如果读取异常抛出异常时返回空字符 * 读取相应输入文件,没有取默认文件 * 如果到达文件尾则将isEnd标志为true */public char nextChar(){if(reader == null){try {fileReader = new FileReader("src/testJava/HelloWord.java");} catch (FileNotFoundException e) {e.printStackTrace();}reader = new BufferedReader(fileReader);}try {if(reader.ready()){setNowChar((char)reader.read());return getNowChar();}} catch (IOException e) {e.printStackTrace();}isEnd = true;return '`';//结束}/** * 接收一个字符判断: * 如果该字符是换行,空字符,制表符则忽略取下一个字符 * 程序总体把分析分成6种种类去分析,并由初始模块根据第一字符原则判断进入哪个类别,.分别是 * 1.字符串:双引号关联起来的字串 * 2.单个字符:单引号关联起来的字符 * 3.注释:行注释以及块注释 * 4.数字:自然数以及小数 * 5.文字(letter):标识符以及关键字 * 6.符号:操作符以及特殊符号或非法字符 */public void step0(char c){while(c == '\n' || c == ' ' || c == '' || c == '\r'){c = nextChar();}if(isEnd){System.out.println("分析结束");try {fileReader.close();reader.close();} catch (IOException e) {e.printStackTrace();}return;}if(c == '\"'){stringStep();}else if(c == '\''){charStep();}else if(c == '/'){noteStep();}else if(Character.isDigit(c)){digitStep();}else if(Character.isLetter(c) || c == '_'){letterStep();}else{signStepOrIllegal();}}/** * 进入字符串步骤 * 过滤第一种缺陷情况就是"\"",但是不能过滤第二重转义字符出现的缺陷. * 因为这种情况不多,所以忽略 */private void stringStep() {token = new StringBuffer(String.valueOf('\"'));char c;do{c = nextChar();token.append(c);if(c == '\"' && !token.toString().equals("\"\\\"")){break;}}while(true);System.out.println(token + " :字符串");step0(nextChar());}/** * 进入单字符步骤 * 可能出现转义字符打印错误,故提供一重修复. * 鉴于深层情况少见,忽略 */private void charStep() {token = new StringBuffer(String.valueOf('\''));char c;do{c = nextChar();token.append(c);if(c == '\'' && !token.toString().equals("'\\'")){break;}}while(true);System.out.println(token + " :单字符");step0(nextChar());}/** * 进入注释步骤 * 行注释以及块注释 */private void noteStep() {token = new StringBuffer(String.valueOf('/'));char c = nextChar();if(c == '/'){//行注释token.append('/');token.append(getRemainLine());}else if(c == '*'){//块注释token.append('*');token.append(getRemainBlock());}else{System.out.println("注释代码未知情况");}System.out.println(token + " :注释");step0(nextChar());}/** * 返回注释块字符串 * 策略是一直扫描直到扫描到*和/符号 *  * @return String */private String getRemainBlock() {StringBuffer buffer = new StringBuffer();char c;char c2;while(true){c = nextChar();if(c == '\t')continue;buffer.append(c);if(c == '*'){c2 = nextChar();if(c2 == '\t')continue;if(c2 == '/'){//如果继*后的符号是斜杠,那么就退出循环buffer.append(c2);break;}buffer.append(c2);}}return buffer.toString();}/** * 返回行注释的字符串 * 扫描策略是直接扫描直到换行符 * @return */private String getRemainLine() {StringBuffer buffer = new StringBuffer();char c;while(true){c = nextChar();if(c == '\n' || c == '\r'){break;}buffer.append(c);}return buffer.toString();}/** * 进入数字过程 * 不包括正负号 * 最多只能出现一个点. */private void digitStep() {boolean dot = false;token = new StringBuffer(String.valueOf(getNowChar()));//把当前数字加入char c = nextChar();while(c == '.' || Character.isDigit(c)){if(c == '.'){if(dot){//就是点已经出现过了break;}dot = true;}token.append(c);//点或者数字都加入字串c = nextChar();}System.out.println(token + " :数字");//跳回步骤0step0(getNowChar());}/** * 进入文字过程 */private void letterStep() {token = new StringBuffer(String.valueOf(getNowChar()));//吧当前的字符串加入char c = nextChar();while(c == '_' || Character.isDigit(c) || Character.isLetter(c)){token.append(c);c = nextChar();}if(keyWork.contains(token.toString())){System.out.println(token + " :关键字");}else{System.out.println(token + " :标识符");}step0(getNowChar());}/** * 进入符号阶段 * 在这里分别区分非法字符 * 操作符,特殊字符 */private void signStepOrIllegal() {token = new StringBuffer();char c = getNowChar();StringBuffer buffer = new StringBuffer(String.valueOf(getNowChar()));while(opera.contains(buffer.toString()) || special.contains(buffer.toString())){token.append(c);c = nextChar();buffer.append(c);}if(token.length() != 0){//非法字符if(special.contains(token.toString())){System.out.println(token + " :特殊字符");}else{System.out.println(token + " :操作符");}}else{System.out.println(getNowChar() + " :非法字符");}step0(getNowChar());}}