lexanalyzer.java

编译器

import java.io.*;
import java.util.*;

public class LexAnalyzer 
{
	private ArrayList<Word> wordList;
	private ArrayList<String> errorList;
	private String[] keyWord={"int","if","else","do","while","read","write"};
	private int keyWordIndex=-1,line =1;
	public boolean isKeyWord(String word)
	{
		boolean isKeyWord=false;
		for(int i=0;i<keyWord.length;i++)
		{
			if(word.equals(keyWord[i]))
			{
				isKeyWord=true;
				keyWordIndex=i;
			}
		}
		return isKeyWord;
	}
	public ArrayList<Word> analysis(String source)
	{
		wordList = new ArrayList<Word>();
		errorList = new ArrayList<String>();
		String tempSource = source.replaceAll("(\t|\\ ){1,}", "\\ ");
		String tempWord="";
		char[] sourceChar = tempSource.toCharArray();
		int charIndex=0,state=1,totalCharIndex=sourceChar.length-1;
		while(charIndex<totalCharIndex)
		{
			switch(state)
			{
				case(1):
				{
					if(Character.isLetter(sourceChar[charIndex]))
					{
						tempWord+=sourceChar[charIndex];
						charIndex++;
						state=3;
					}
					else if(Character.isDigit(sourceChar[charIndex]))
					{
						tempWord+=sourceChar[charIndex];
						charIndex++;
						state=8;
					}
					else if(Character.isWhitespace(sourceChar[charIndex])||Character.isISOControl(sourceChar[charIndex]))//'\n'是whiteSpace?
					{
						if(sourceChar[charIndex]=='\n')line++;
						tempWord="";
						charIndex++;
						state=1;
					}
					else
					{
						switch(sourceChar[charIndex])
						{
						case('+'):state=6;
								  tempWord+=sourceChar[charIndex];
								  charIndex++;
								  break;
						case('-'):state=7;
								  tempWord+=sourceChar[charIndex];
						          charIndex++;
						          break;
						case('*'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"MULTYPLY",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('/'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"DIVISION",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case(','):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"COMM",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case(';'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"SEMICOLON",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('('):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"LEFT(",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case(')'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"RIGHT)",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('.'):tempWord+=sourceChar[charIndex];
				  		  		  wordList.add(new Word(tempWord,"DOT",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('"'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"DOUBLECOMM",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('['):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"LEFT[",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case(']'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"RIGHT]",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('{'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"LEFT{",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('}'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"RIGHT}",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('<'):state=5;
								  tempWord+=sourceChar[charIndex];
								  charIndex++;
						          break;
						case('>'):tempWord+=sourceChar[charIndex];
						  		  wordList.add(new Word(tempWord,"LARGER",line));
						          tempWord="";
						          charIndex++;
						          state=1;
						          break;
						case('='):state=4;
								  tempWord+=sourceChar[charIndex];
								  charIndex++;
								  break;
						default:String errorMessage = "Unexpected operator "+sourceChar[charIndex]+" in line:"+line;
								errorList.add(errorMessage);
								charIndex++;
								break;
						}
					}
					break;
				}
				case(3):
				{
					int tempState = ((Character.isLetterOrDigit(sourceChar[charIndex])
									  ||sourceChar[charIndex]=='_')?3:0);
					if(Character.isWhitespace(sourceChar[charIndex])
							||Character.isISOControl(sourceChar[charIndex])) tempState=1;
					switch(tempState)
					{
						case(0): 
							state=1;
							if(isKeyWord(tempWord))
							{
								wordList.add(new Word(tempWord,keyWord[keyWordIndex],line));
							}
							else
							{
								wordList.add(new Word(tempWord,"ID",line));
							}
							tempWord="";
							break;
						case(3):
							tempWord += sourceChar[charIndex];
							charIndex++;
							state = 3;
							break;
						case(1):
							if(sourceChar[charIndex-1]=='_')
							{
								errorList.add("Identifier should not end with '_' in line: "+line);
								tempWord="";
								if(sourceChar[charIndex]=='\n')line++;
								charIndex++;
								state=1;
								break;
							}
							else
							{
								if(isKeyWord(tempWord))
								{
									wordList.add(new Word(tempWord,keyWord[keyWordIndex],line));
								}
								else
								{
									wordList.add(new Word(tempWord,"ID",line));
								}
								tempWord = "";
								if(sourceChar[charIndex]=='\n')line++;
								charIndex++;
								state=1;
								break;
							}
						default:state=10;
					}
					break;
				}
				case(4):
				{
					if(sourceChar[charIndex]=='=')
					{
						tempWord+=sourceChar[charIndex];
						wordList.add(new Word(tempWord,"EQUAL",line));
						tempWord="";
						charIndex++;
					}
					else
					{
						wordList.add(new Word(tempWord,"ASSIGN",line));
						tempWord="";
					}
					state=1;
					break;
				}
				case(5):
				{
					if(sourceChar[charIndex]=='>')
					{
						tempWord+=sourceChar[charIndex];
						wordList.add(new Word(tempWord,"NOTEQUAL",line));
						tempWord="";
						charIndex++;
					}
					else
					{
						wordList.add(new Word(tempWord,"LESS",line));
						tempWord="";
					}
					state=1;
					break;
				}
				case(6):
				{
					if(sourceChar[charIndex]=='+')
					{
						tempWord+=sourceChar[charIndex];
						wordList.add(new Word(tempWord,"AA",line));
						tempWord="";
						charIndex++;
					}
					else
					{
						wordList.add(new Word(tempWord,"ADD",line));
						tempWord="";
					}
					state=1;
					break;
				}
				case(7):
				{
					if(sourceChar[charIndex]=='-')
					{
						tempWord+=sourceChar[charIndex];
						wordList.add(new Word(tempWord,"MM",line));
						tempWord="";
						charIndex++;
					}
					else
					{
						wordList.add(new Word(tempWord,"MINUS",line));
						tempWord="";
						
					}
					state=1;
					break;
				}
				case(8):
				{
					int tempState=(Character.isDigit(sourceChar[charIndex])?1:0);
					switch(tempState)
					{
					case(1):
							tempWord+=sourceChar[charIndex];
							charIndex++;
							state=8;
							break;
					case(0):
							if(Character.isLetter(sourceChar[charIndex]))
							{
								errorList.add("Identifier should start with a letter in line: "+line);
								tempWord="";
								state=1;
								break;
							}
							else
							{
								wordList.add(new Word(tempWord,"NUMBER",line));
								tempWord="";
								state=1;
								break;
							}
					}
					break;
				}
				case(10):
				{
					System.out.println("Should start with letter.");
					charIndex++;
					break;
				}
			}
		}
		wordList.add(new Word("","#",0));
		return wordList;
	}
	public ArrayList<String> getErrorList()
	{
		return errorList;
	}
}