Why the getMethod for List<String> is not printing out the values in another Method?

I have been dealing with this problem for the longest time and I really hope someone can tell me what's happening and how to make the getMethod for List<String> returns the values.

Code:

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public void insertTutor_Subject(int tutor_id, List<String> subjNames) throws MyDataException {
               
                Tutor m = new Tutor();
                System.out.println(tutor_id); //this will return the generated_id
                System.out.println(m.getSubjects());//not able to print out
try {
                        //openConnection();               
                        PreparedStatement ps3 = connection.prepareStatement("INSERT INTO project.tutor_subject(tutor_id, subjectName) VALUES (?, ?);");
                        ps3.setInt(1, tutor_id);
                        //System.out.println(m.getTutor_id()); //m.getTutor_id() will give you 0
                        ps3.setObject(2, m.getSubjects());
                        System.out.println(m.getSubjects());
                        ps3.addBatch();
                        ps3.setInt(1, tutor_id);
                        ps3.setObject(2, m.getSubjects());
                        ps3.addBatch();

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At my controller :

Code:

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String[] subj = request.getParameterValues("subject");
                        List<String>subjs = new ArrayList<String>(Arrays.asList(subj));
                    m4.setSubjects(subjs);
                    System.out.println(m4.getSubjects());        // able to see the values

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My first question is m4.getSubjects at the controller is able to return the value so why is it not showing up at the insertTutor_Subject method?

My 2nd question is do I still need to OpenConnection(static method for JDBC Connection) in order for the insertion to work?

My last question is if the above - using Batch to insert the List<String> ? Is there anything wrong with this method ?

Thanks

Can you make and post a small complete program that compiles, executes and shows the problem?

Please wrap all posted code in code tags to preserve formatting.

The reason is that in the following method you are declaring a new Tutor object, but aren't populating it.

Code:

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public void insertTutor_Subject(int tutor_id, List<String> subjNames) throws MyDataException {
               
                Tutor m = new Tutor();
                System.out.println(tutor_id); //this will return the generated_id
                System.out.println(m.getSubjects());//not able to print out -- YES, because it's empty

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The following works because you call m4.setSubjects (presumably m4 is an instance of the Tutor object).

Code:

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String[] subj = request.getParameterValues("subject");
                        List<String>subjs = new ArrayList<String>(Arrays.asList(subj));
                    m4.setSubjects(subjs); // SETTING the VALUES
                    System.out.println(m4.getSubjects());        // able to see the values

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Do you have to call setSubjects() first?

Code:

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public void insertTutor_Subject(int tutor_id, List<String> subjNames) throws MyDataException {
               
                Tutor m = new Tutor();
                System.out.println(tutor_id);
                m.setSubjects(subjNames);
                System.out.println(m.getSubjects());

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