Cannot assign an ArrayList to an empty ArrayList



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Sarbu Diana
Cannot assign an ArrayList to an empty ArrayList
1 Answer(s)      5 years and 3 months ago
Posted in : Java Beginners

I have a java file, in which a method returns an ArrayList. This ArrayList is supposed to contain all the Student object which are in X year. public ArrayList<Student> studByYear(int value){

ArrayList<Student> students = StudentsManager.getInstance().getStudent√Ę‚?¨¬¶
Iterator<Student> itr = students.iterator();

ArrayList<Student> found_stud = new ArrayList<Student>(); 

while (itr.hasNext()) {
Student element =;

if(element.getYear() == value){
return null;
return found_stud;


I want to do something like this:

ArrayList<Student>found_list = new ArrayList<Student>();

if(year > 0){ if year typed in the html form is > 0

//found_list = StudentsManager.getInstance().studByYear√Ę‚?¨¬¶


getInstance() is a singleton of StudentsManager. I access StudentsManager's methods statically.

studByYear(year); returns an ArrayList of all the students that are in the year "year".

I already tried with:

 a) List<Integer> newList = new ArrayList<Integer>(oldList); here it could not compile
    b) Collections.copy(arrayList2,arrayList1); here I got exception :|
View Answers

June 30, 2012 at 1:59 AM

I mean I want to save in the ArrayList, called foundlist, the result I receive from calling the method StudentsManager.getInstance().studByYear(year); This method returns an ArrayList of students that are in a particular year. I will put foundlist in a table in html.


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