search.java

对一个文件夹下面的doc和txt文件（文件夹下不包含文件夹）中的内容建立索引并实现了搜索功能。（代码有缺陷

package src;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;

import org.tartarus.snowball.SnowballStemmer;
import org.tartarus.snowball.ext.englishStemmer;
public class Search {
	
	/**
	 * @param args
	 */
	public Search() {
		new Index();
	}
	public String search(String inString){
		Stack<StringTokenizer> data = new Stack<StringTokenizer>();
		Stack<String> operator = new Stack<String>();
		operator.push("#");
		String output = "";
		int countparentheses = 0;//in order to check the formula
		StringTokenizer test = new StringTokenizer(inString," ()#",true);//in order to check the formula
		/*
		 * exception handler for wrong formula.some of exception handlers are enbeded in the mian method program
		 */
		while(test.hasMoreTokens()){
			String o = test.nextToken();
			if(o.equals("("))
					countparentheses ++;
			else if (o.equals(")"))
				countparentheses --;
		}	
		if (countparentheses != 0){
			return ("The formula is not correct,please check your input \"" + inString + "\"");
		}
		//alter and compute
		StringTokenizer tokens = new StringTokenizer(inString + "#"," ()#",true);
		if (tokens.countTokens() == 1){
			atomicQuery(tokens.nextToken());
		}
		else {
			while(tokens.hasMoreTokens()){
				String temp = tokens.nextToken();
				/*
				 * deal with the operant
				 */
				if(!temp.equals("AND") && !temp.equals("OR") && !temp.equals("NOT") && !temp.equals("(") && !temp.equals(")") && !temp.equals("#") && !temp.equals(" ")){
					data.push(atomicQuery(temp));
					output += temp + " ";
				}
				/*
				 * deal with the bracket
				 */
				else if(temp.equals( ")")){
					for(String o =operator.pop();!operator.isEmpty() && !o.equals("(");o = operator.pop()){
						if (o.equals("AND")){
							StringTokenizer behind = data.pop();
							StringTokenizer ahead = data.pop();
							data.push(and(ahead,behind));
						}
						else if (o.equals("OR")){
							StringTokenizer behind = data.pop();
							StringTokenizer ahead = data.pop();
							data.push(or(ahead,behind));
						}
						else if (o.equals("NOT")){
							StringTokenizer behind = data.pop();
							data.push(not(behind));
						}
						output += o + " ";
						o = operator.pop();
					}
				}
				else if(temp.equals("(")){
					operator.push(temp);
				}
				/*
				 *deal with the operator
				 */
				else{
					if(!operator.isEmpty()){
						String o = operator.pop();
						while(true){
							if (operator.isEmpty() || icp(temp)  >  isp(o)){
								operator.push(o);
								break;
								}
							if (o.equals("AND")){
								StringTokenizer behind = data.pop();
								StringTokenizer ahead = data.pop();
								data.push(and(ahead,behind));
							}
							else if (o.equals("OR")){
								StringTokenizer behind = data.pop();
								StringTokenizer ahead = data.pop();
								data.push(or(ahead,behind));
							}
							else if (o.equals("NOT")){
								StringTokenizer behind = data.pop();
								data.push(not(behind));
							}
							output += o + " ";
							o = operator.pop();
						}
					}
					operator.push(temp);
				}
			}
		}
		String result = "";
		StringTokenizer endTokens = data.pop();
		while (endTokens.hasMoreTokens()){
			result += endTokens.nextToken();
		}
		return result;
//		return "The correct answer of " + inString + " is\n" + output + "= " + data.pop() ;
}
	/*
	 * in stack priority
	 */
	private int isp(String sign){
		if(sign.equals("AND") || sign.equals("OR") || sign.equals("NOT"))
			return 3;
		else if(sign.equals("("))
			return 1;
		else if(sign.equals(")"))
			return 4;
		else 
			return 0;
	}
	/*
	 * in coming priority
	 */
	private int icp(String sign){
		if (sign.equals("AND") || sign.equals("OR") || sign.equals("NOT"))
			return 2;
		else if (sign.equals("("))
			return 4;
		else if (sign.equals(")"))
			return 1;
		else 
			return 0;
	} 
	private StringTokenizer and(StringTokenizer ahead,StringTokenizer behind){
		String result = "";
		TreeSet<String> former = new TreeSet<String>();
		while (ahead.hasMoreTokens()){
			former.add(ahead.nextToken());
		}
		while (behind.hasMoreTokens()){
			String token = behind.nextToken();
			if (former.contains(token)){
				result += token + "|";
			}
		}
		return new StringTokenizer(result,"|");	
	}
	private StringTokenizer or(StringTokenizer ahead,StringTokenizer behind){
		String result = "";
		TreeSet<String> former = new TreeSet<String>();
		while (ahead.hasMoreTokens()){
			String token = behind.nextToken();
			former.add(token);
			result += token + "|";
		}
		while (behind.hasMoreTokens()){
			String token = behind.nextToken();
			if (!former.contains(token)){
				result += token + "|";
			}
		}
		return new StringTokenizer(result,"|");	
	}
	private StringTokenizer not(StringTokenizer behind){
		String result = "";
		File directory = new File("test-files");
		File[] files = directory.listFiles();
		TreeSet<String> latter = new TreeSet<String>();
		while (behind.hasMoreTokens()){
			latter.add(behind.nextToken());
		}
		for (int i = 0;i < files.length;i ++){
			String fileName = files[i].getPath().substring(files[i].getPath().indexOf("\\") + 1);
			if (!latter.contains(fileName)){
				result += fileName + "|";
			}
		}
		return new StringTokenizer(result,"|");
	}
	private StringTokenizer atomicQuery(String keyword){
		StringTokenizer line = null;
		try{
			BufferedReader br = new BufferedReader(new FileReader("index"));
			line = new StringTokenizer(br.readLine(),":|");
			SnowballStemmer stemmer = new englishStemmer();
			stemmer.setCurrent(keyword.toLowerCase());
			stemmer.stem();
			if (stemmer.getCurrent().equalsIgnoreCase(line.nextToken()));
		}catch(IOException e){
			System.out.println(e);
		}
		return line;
	}
	public static void main(String args[]){
		Search s = new Search();
		System.out.println(s.search("exception"));
	}
}