Java朴素贝叶斯算法 Java实现的朴素贝叶斯算法示例

package NB;
/**
 * 训练样本的属性 javaBean
 *
 */
public class JavaBean {
 int age;
 String income;
 String student;
 String credit_rating;
 String buys_computer;
 public JavaBean(){
 }
public JavaBean(int age,String income,String student,String credit_rating,String buys_computer){
  this.age=age;
  this.income=income;
  this.student=student;
  this.credit_rating=credit_rating;
  this.buys_computer=buys_computer;
}
public int getAge() {
  return age;
}
public void setAge(int age) {
  this.age = age;
}
public String getIncome() {
  return income;
}
public void setIncome(String income) {
  this.income = income;
}
public String getStudent() {
  return student;
}
public void setStudent(String student) {
  this.student = student;
}
public String getCredit_rating() {
  return credit_rating;
}
public void setCredit_rating(String credit_rating) {
  this.credit_rating = credit_rating;
}
public String getBuys_computer() {
  return buys_computer;
}
public void setBuys_computer(String buys_computer) {
  this.buys_computer = buys_computer;
}
@Override
public String toString() {
  return "JavaBean [age=" + age + ", income=" + income + ", student="
      + student + ", credit_rating=" + credit_rating + ", buys_computer="
      + buys_computer + "]";
}
}

package NB;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.ArrayList;
public class TestNB {
  /**data_length
   * 算法的思想
   */
  public static ArrayList<JavaBean> list = new ArrayList<JavaBean>();;
  static int data_length=0;
  public static void main(String[] args) {
    // 1.读取数据，放入list容器中
    File file = new File("E://test.txt");
    txt2String(file);
    //数据测试样本
    testData(25,"Medium","Yes","Fair");
  }
  // 读取样本数据
  public static void txt2String(File file) {
    try {
      BufferedReader br = new BufferedReader(new FileReader(file));// 构造一个BufferedReader类来读取文件
      String s = null;
      while ((s = br.readLine()) != null) {// 使用readLine方法，一次读一行
        data_length++;
        splitt(s);
      }
      br.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
  // 存入ArrayList中
   public static void splitt(String str){
      String strr = str.trim();
      String[] abc = strr.split("[\\p{Space}]+");
      int age=Integer.parseInt(abc[0]);
      JavaBean bean=new JavaBean(age, abc[1], abc[2], abc[3], abc[4]);
      list.add(bean);
    }
   // 训练样本，测试
   public static void testData(int age,String a,String b,String c){
     //训练样本
     int number_yes=0;
     int bumber_no=0;
     // age情况 个数
     int num_age_yes=0;
     int num_age_no=0;
     // income
     int num_income_yes=0;
     int num_income_no=0;
     // student
     int num_student_yes=0;
     int num_stdent_no=0;
     //credit
     int num_credit_yes=0;
     int num_credit_no=0;
     //遍历List 获得数据
     for(int i=0;i<list.size();i++){
      JavaBean bb=list.get(i);
      if(bb.getBuys_computer().equals("Yes")){ //Yes
        number_yes++;
        if(bb.getIncome().equals(a)){//income
          num_income_yes++;
        }
        if(bb.getStudent().equals(b)){//student
          num_student_yes++;
        }
        if(bb.getCredit_rating().equals(c)){//credit
          num_credit_yes++;
        }
        if(bb.getAge()==age){//age
          num_age_yes++;
        }
      }else {//No
        bumber_no++;
        if(bb.getIncome().equals(a)){//income
          num_income_no++;
        }
        if(bb.getStudent().equals(b)){//student
          num_stdent_no++;
        }
        if(bb.getCredit_rating().equals(c)){//credit
          num_credit_no++;
        }
        if(bb.getAge()==age){//age
          num_age_no++;
        }
      }
     }
      System.out.println("购买的历史个数:"+number_yes);
      System.out.println("不买的历史个数:"+bumber_no);
      System.out.println("购买+age:"+num_age_yes);
      System.out.println("不买+age:"+num_age_no);
      System.out.println("购买+income:"+num_income_yes);
      System.out.println("不买+income:"+num_income_no);
      System.out.println("购买+stundent:"+num_student_yes);
      System.out.println("不买+student:"+num_stdent_no);
      System.out.println("购买+credit:"+num_credit_yes);
      System.out.println("不买+credit:"+num_credit_no);
      //// 概率判断
      double buy_yes=number_yes*1.0/data_length; // 买的概率
      double buy_no=bumber_no*1.0/data_length; // 不买的概率
      System.out.println("训练数据中买的概率:"+buy_yes);
      System.out.println("训练数据中不买的概率:"+buy_no);
      /// 未知用户的判断
      double nb_buy_yes=(1.0*num_age_yes/number_yes)*(1.0*num_income_yes/number_yes)*(1.0*num_student_yes/number_yes)*(1.0*num_credit_yes/number_yes)*buy_yes;
      double nb_buy_no=(1.0*num_age_no/bumber_no)*(1.0*num_income_no/bumber_no)*(1.0*num_stdent_no/bumber_no)*(1.0*num_credit_no/bumber_no)*buy_no;
      System.out.println("新用户买的概率:"+nb_buy_yes);
      System.out.println("新用户不买的概率:"+nb_buy_no);
      if(nb_buy_yes>nb_buy_no){
        System.out.println("新用户买的概率大");
      }else {
        System.out.println("新用户不买的概率大");
      }
   }
}