HashMap accessing same ArrayList

Question

I am trying the following to update the HashMap with new value of student, please check where I'm missing something.

ArrayList<Student> tempStudentList = XMLParser.studentHashMap.get(currentSectionName);

if(studentList==null)
{

    Log.v(CURRENT_SCREEN,"created another student list for section name:"+currentSectionName);
    tempStudentList = new ArrayList<Student>();

} 
Log.v(CURRENT_SCREEN,"Added student to the list");

tempStudentList.add(currentStudent);

XMLParser.studentHashMap.put(currentSectionName, tempStudentList);

You haven't given us nearly enough context - we don't know what's going wrong, for example, or where student is coming from. — Jon Skeet
– Jon Skeet, Commented Jun 13, 2011 at 12:38

KARASZI István · Accepted Answer · 2011-06-13 12:37:58Z

3

I think you wanted to write tempStudentList instead of studentList at the null check.

answered Jun 13, 2011 at 12:37

KARASZI István

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Comments

seanhodges · Accepted Answer · 2011-06-13 13:35:45Z

1

You're checking the wrong variable for null. Also, Java collections are mutable, the array in studentHashMap is manipulated directly so you don't need to perform another put after every query on your map:

ArrayList<Student> tempStudentList = XMLParser.studentHashMap.get(currentSectionName);

if(tempStudentList == null)
{
    Log.v(CURRENT_SCREEN, "created another student list for section name:"+currentSectionName);
    tempStudentList = new ArrayList<Student>();
    XMLParser.studentHashMap.put(tempStudentList);
} 

tempStudentList.add(currentStudent);
Log.v(CURRENT_SCREEN,"Added student to the list");

answered Jun 13, 2011 at 13:35

seanhodges

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