java.lang.IndexOutOfBoundsException：使用ArrayList时索引：0，大小：0

Question

I m trying to store all these elements and im getting error like java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 and I'm not sure what my mistakes are.

public List<AddUserInformation> insertData(AddUserDetail user) {
    List<AddUserInformation> inserted = null;
    try{
        List<AddUserInformation> addUserInformation = new ArrayList<AddUserInformation>() ;
        ArrayList accName = new ArrayList();

        for (int i = 0; i < user.getListofaccounts().toArray().length ; i++) {
            accName.add(user.getListofaccounts().get(i).getAccountName());                  
        }

        List<AddUserInformation> addUserInformation1 = new ArrayList<AddUserInformation>();
        for (int i = 0; i< accName.toArray().length; i++) {   
            addUserInformation1.get(i).setUserID(user.getUserId());
            addUserInformation1.get(i).setUsername(user.getUsername());
            addUserInformation1.get(i).setPassword(user.getPassword());
            addUserInformation1.get(i).setEmailid(user.getEmailid()); 
            List<AddUserAccountDetails> adduseraccountdetails = new ArrayList<>();
            addUserInformation1.get(i).setAccountName(user.getListofaccounts().get(i).getAccountName());
            addUserInformation1.get(i).setPermission_id(user.getListofaccounts().get(i).getPermission_id());
        }
        inserted = adduserInformationDao.saveAddUserInfo(addUserInformation1);

    } catch (Exception e) {
        LOGGER.error("Exception in adding of account to a user " + user.getUsername(), e);
    }
    return inserted;
}

The thing is accName contains number of accounts lets say 'n' as list and in the second "for" loop finally to replaces new values and showing last list values.

Answer 1

The statement:

List<AddUserInformation> addUserInformation1 = new ArrayList<AddUserInformation>();

creates a new empty ArrayList , so when you write addUserInformation1.get(i) in the for loop, you are trying to access the element at index 0 but the list is still empty (no element at 0 ), so you get the exception.

You must add something to your list (eg, invoking add(...) method) before trying to get(...) elements.

Answer 2

As Robert mentioned, you are trying to access an element that is not exist.

Note: The List<AddUserAccountDetails> adduseraccountdetails = new ArrayList<>(); is never in use ..

You can create an object of class AddUserInformation then add it to your list like this:

    public List<AddUserInformation>  insertData(AddUserDetail user) {
       List<AddUserInformation>  inserted = null;
        try{
            List<AddUserInformation> addUserInformation = new ArrayList<AddUserInformation>() ;
            ArrayList accName = new ArrayList();

            for( int i = 0; i < user.getListofaccounts().toArray().length ; i++ ) {
               accName.add(user.getListofaccounts().get(i).getAccountName());   
            }
            List<AddUserInformation> addUserInformation1 = new ArrayList<AddUserInformation>();
            for(int i = 0; i< accName.toArray().length; i++) {   
                AddUserInformation obj = new AddUserInformation ();
                obj.setUserID(user.getUserId());
                obj.setUsername(user.getUsername());
                obj.setPassword(user.getPassword());
                obj.setEmailid(user.getEmailid()); 
                obj.setAccountName(user.getListofaccounts().get(i).getAccountName());
                obj.setPermission_id(user.getListofaccounts().get(i).getPermission_id());
                addUserInformation1.add(obj);
                }
            inserted = adduserInformationDao.saveAddUserInfo(addUserInformation1);
          }catch (Exception e) {
        LOGGER.error("Exception in adding of account to a user " + user.getUsername(), e);
        }
        return inserted;
    }