通过使用字符串和列表作为参数的散列图迭代

Question

我有一个场景，我必须通过HashMap循环来检查空值并生成一个空的bean。空bean将再次添加到新地图。

for (String course_date : shiftSet) { 
     Bean courseBean = null; 
     boolean valueExists = false; 

       for (Entry<String, List<Bean>> entry: courseMap.entrySet()){ 

        String studentDetail = entry.getKey(); 
        String [] studentSet = StringUtils.getArray(studentDetail , ","); 
        String studentId = studentSet[0]; 
        String courseId = studentSet[1]; 

        for(Bean resultBean : entry.getValue()){ 

         if(course_date.equalsIgnoreCase(resultBean.getCourseDate()){ 
          valueExists = true; 
         } 
       } 
         if(!valueExists) { 
          courseBean = new Bean(); 
          courseBean.setStudent(studentId); 
          courseBean.setCourse(courseId); 
          List<Bean> courseList = entry.getValue(); 
          courseList.add(courseBean); 
          outputMap.put(studentId+courseId, courseList); 
         } 
      } 
     } 

即使不满足内部环路条件，布尔值也始终为真。

任何人都可以提出一个更好的解决方案来实现所需的输出？

在此先感谢

Answer 1

主要问题是您的valueExists变量在for循环之前被初始化，每个验证所需的位置。将其重写为：

//declare it here (regardless this "initial" value) 
boolean valueExists = false; 
for (Entry<String, List<Bean>> entry: courseMap.entrySet()) { 
    //initialize it here 
    valueExists = false; 
    //... 
    for (Bean resultBean : entry.getValue()) { 
     if(course_date.equalsIgnoreCase(resultBean.getCourseDate()){ 
      valueExists = true; 
      //also, add a break here since you already found the value 
      //you don't need to keep iterating through the rest of items 
      break; 
     } 
    } 
    if (valueExists) { 
     //... 
    } 
} 

Answer 2

你有2个变量名称相同value。一个是String另一个布尔值。我想这种含糊不清让我们，你自己和编译器感到困惑。实际上你的代码甚至不应该编译。

Answer 3

有一次，您发现日期匹配，然后跳出for循环。因为，您正在迭代列表，因此只有当bean列表中的最后一个条目为false时，您的布尔变量才会为false。

看到代码审查，可能的工作液

for (String course_date : shiftSet) { 
     Bean courseBean = null; 

      for (Entry<String, List<Bean>> entry: courseMap.entrySet()){ 

       // Declare this boolean variable inside, since you are dealing with a single entry in the map at a time. 
       boolean matchCourseDate = false; 

       //Declare variable with more meaningful naming conventions. 
       String key = entry.getKey(); 
       String [] studentSet = StringUtils.getArray(key, ","); 
       String studentId = studentSet[0]; 
       String courseId = studentSet[1]; 

       // Since, you are iterating over the list, make sure once you found the date match break out if this loop 
       for(Bean resultBean : entry.getValue()){ 
        if(course_date.equalsIgnoreCase(resultBean.getCourseDate()){ 
         matchCourseDate = true; 
        } 

        // If the match is found, break. Otherwise, keep going. 
        if(matchCourseDate) 
         break; 
       } 

       // If no match is found, then create a new bean and put it into output map. 
        if(!matchCourseDate) { 
         courseBean = new Bean(); 
         courseBean.setStudent(studentId); 
         courseBean.setCourse(courseId); 
         List<Bean> courseList = entry.getValue(); 
         courseList.add(courseBean); 
         outputMap.put(studentId+courseId, courseList); 
        } 
     } 
    }