基于朴素贝叶斯的垃圾邮件检测

来源：互联网发布：已知矩阵计算A5次α 编辑：程序博客网时间：2024/05/01 20:08
package cn.zhf.test;import java.io.*;import java.util.*;public class SpamMailDetection {    public static final String BASE_PATH = "C:\\Users\\zhf\\Desktop\\mail";    public static final String SPAM_PATH = BASE_PATH + "\\train_illegal.txt";//垃圾邮件语料    public static final String OK_PATH = BASE_PATH + "\\train_legal.txt";//正常邮件语料    public static final String EMAIL_PATH = BASE_PATH + "\\to_judge.txt";//要判别的邮件    public static final String DICT_PATH = BASE_PATH + "\\dict.txt";//分词用的词典    public static void main(String[] args) {    SpamMailDetection smc = new SpamMailDetection();        //<word,(word/NonSpamCorpus)>        Map<String, Double> okmap = smc.createMailMap(OK_PATH);        //<word,(word/SpamCorpus)>        Map<String, Double> spammap = smc.createMailMap(SPAM_PATH);        Map<String, Double> ratemap = smc.createSpamProbabilityMap(spammap, okmap);        double probability = smc.judgeMail(EMAIL_PATH, ratemap);        if (probability > 0.5)//概率大于0.5则判定为垃圾            System.out.println("It's an ok mail.");        else            System.out.println("It's a spam mail.");    }    /**     * 给定邮件,分词,根据分词结果判断是垃圾邮件的概率      * P(Spam|t1,t2,t3……tn)=（P1*P2*……PN）/(P1*P2*……PN+(1-P1)*(1-P2)*……(1-PN))     */    public double judgeMail(String emailPath, Map<String, Double> ratemap) {        List<String> list = segment(readFile(emailPath));        double rate = 1.0;        double tempRate = 1.0;        for (String str : list) {            if (ratemap.containsKey(str)) {                double tmp = ratemap.get(str);                tempRate *= 1 - tmp;                rate *= tmp;            }        }        return rate / (rate + tempRate);    }    /**     * 从给定的垃圾邮件、正常邮件语料中建立map <切出来的词,出现的频率>     */    public Map<String, Double> createMailMap(String filePath) {        String str = readFile(filePath);        List<String> list = segment(str);        Map<String, Integer> tmpmap = new HashMap<String, Integer>();        Map<String, Double> retmap = new HashMap<String, Double>();        double rate = 0.0;        int count = 0;        for (String s : list) {            tmpmap.put(s, tmpmap.containsKey(s) ? count + 1 : 1);        }        for (Iterator iter = tmpmap.keySet().iterator(); iter.hasNext();) {            String key = (String) iter.next();            rate = tmpmap.get(key) / list.size();            retmap.put(key, rate);        }        return retmap;    }    /**     * 建立map,<str,rate> 邮件中出现ti时,该邮件为垃圾邮件的概率     * P( Spam|ti) =P2(ti )/((P1 (ti ) +P2 ( ti ))     */    public Map<String, Double> createSpamProbabilityMap(Map<String, Double> spammap,            Map<String, Double> okmap) {        Map<String, Double> retmap = new HashMap<String, Double>();        for (Iterator iter = spammap.keySet().iterator(); iter.hasNext();) {            String key = (String) iter.next();            double rate = spammap.get(key);            double allRate = rate;            if (okmap.containsKey(key)) {                allRate += okmap.get(key);            }            retmap.put(key, rate / allRate);        }        return retmap;    }    /**     * 中文分词     */    public List<String> segment(String str) {        Map<String, Integer> map = loadDict();        List<String> list = new ArrayList<String>();        int len = str.length();        String term;        int maxSize = 6;        int i = 0, j = 0;        while (i < len) {            int n = i + maxSize < len ? i + maxSize : len + 1;            boolean findFlag = false;            for (j = n - 1; j > i; j--) {                term = str.substring(i, j);                if (map.containsKey(term)) {                    list.add(term);                    findFlag = true;                    i = j;                    break;                }            }            if (findFlag == false)                i = j + 1;        }        return list;    }    /**     * 加载词典文件     */    public Map<String, Integer> loadDict() {        Map<String, Integer> map = new HashMap<String, Integer>();        String[] str;        try {            BufferedReader br = new BufferedReader(new InputStreamReader(                    new FileInputStream(new File(DICT_PATH)), "gbk"));            String tmp = "";            while ((tmp = br.readLine()) != null) {                str = tmp.split("\t");                map.put(str[0], 0);            }            br.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        return map;    }    /**     * 读文件     */    public String readFile(String filePath) {        String str = "";        try {            BufferedReader br = new BufferedReader(new InputStreamReader(                    new FileInputStream(new File(filePath)), "gbk"));            String tmp = "";            while ((tmp = br.readLine()) != null)                str += tmp;            br.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        return str;    }}
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