java - 使用字符串和列表作为参数迭代 HashMap

Question

我有一个场景，我必须循环遍历 HashMap 来检查空值并生成一个空 bean。空 bean 将再次添加到新映射中。

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);
                         }
            }
        }

即使不满足内循环条件， boolean 值也始终为 true。

任何人都可以提出更好的解决方案来实现所需的输出吗？

提前致谢

Answer 1

主要问题是您的 valueExists 变量在每次验证都需要的 for 循环之前初始化。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) {
        //...
    }
}