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POupdating JList with DefaultListModel
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copied!<p>I am using an embedded database to query the name of an entry and put it in a <code>JList</code>. When the program runs, the list is populated fine.</p> <p>I have made a function that is supposed to initialize and refresh the list called <code>populateList()</code>.</p> <p>Here are the relevant parts of my code:</p> <pre><code>public class GUI extends JFrame{ private int maxBankNr; private BankAccountDAO bankAccountDAO; private DBManager dbm; ... public GUI(){ initComponents(); //sets up the Swing GUI this.dbm = new DBManager(); this.bankAccountDAO = dbm.getBankAccountDAO(); ... populateList(); } private void populateList(){ updateAll = false; //this seems to stop baAccountListValueChanged from throwing an exception this.maxBankNr = bankAccountDAO.getMaxBankNr(); //max number of bank accounts in database BankAccount ba; DefaultListModel dlm = new DefaultListModel(); baAccountList.setModel(dlm); for(int i = 1; i <= this.maxBankNr; i++){ ba = bankAccountDAO.getBankAccount(i); dlm.addElement(ba.getName()); } updateAll = true; } ... private void baRefreshButtonActionPerformed(java.awt.event.ActionEvent evt){ populateList(); } ... </code></pre> <p>My problem is that <code>populateList()</code> works fine when the program starts, but when it is called from <code>baRefreshButtonActionPerformed</code>, it appears to do nothing. The list stays exactly the same.</p> <p>I have tried lots of different approaches, like using a Vector, using <code>JList.setListData()</code>, revalidating, validating and repainting all relevant containers. I have also tried using different types of <code>ListModel</code>.</p> <p>Also, I have read that calling <code>fireContentsChanged()</code> should work, but <code>DefaultListModel</code> doesn't allow it, and I'm sure it gets called automatically anyway.</p> <p>I have spent hours looking for a fix, most sites I've visited say the same things that I have tried, although none of them are working.</p> <p>I hope this is enough information, let me know if you need to know anything else, thanks.</p> <p><strong>EDIT</strong> I have finally managed to fix this, much to my relief :D</p> <p>It had nothing to do with my <strong>ListModel</strong> at all, but my <strong>BankAccountDAO</strong> class. This is the old version:</p> <pre><code>package com.accounts; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class BankAccountDAO { private String insertBankAccountSQL = "INSERT INTO accounts.bankaccounts(bankNr, sortCode, accountNumber, balance, interest, details, name) " + "VALUES (?, ?, ?, ?, ?, ?, ?)"; private String getBankAccountSQL = "SELECT bankNr, sortCode, accountNumber, balance, interest, details, name " + "FROM accounts.bankaccounts WHERE bankNr = ?"; private Connection conn = null; private PreparedStatement pstmt = null; private int maxBankNr = 0; public BankAccountDAO(Connection theConn){ this.conn = theConn; try{ this.pstmt = conn.prepareStatement(getBankAccountSQL); Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery("SELECT MAX(bankNr) FROM accounts.bankaccounts"); if(rs.next()){ maxBankNr = rs.getInt(1); } rs.close(); stmt.close(); }catch(SQLException se){ printSQLException(se); } } public int getMaxBankNr(){ return(this.maxBankNr); } public void insertBankAccount(int bankNr, int sortCode, int accountNumber, double balance, double interest, String details, String name){ PreparedStatement ins = null; try{ ins = conn.prepareStatement(insertBankAccountSQL); ins.setInt(1, bankNr); ins.setInt(2, sortCode); ins.setInt(3, accountNumber); ins.setDouble(4, balance); ins.setDouble(5, interest); ins.setString(6, details); ins.setString(7, name); ins.execute(); }catch(SQLException se){ printSQLException(se); } } public BankAccount getBankAccount(int targetBankNr){ BankAccount ba = null; try{ pstmt.clearParameters(); pstmt = conn.prepareStatement(getBankAccountSQL); pstmt.setInt(1, targetBankNr); ResultSet rs = pstmt.executeQuery(); if(rs.next()){ int bankNr = rs.getInt("bankNr"); int sortCode = rs.getInt("sortCode"); int accountNumber = rs.getInt("accountNumber"); double balance = rs.getDouble("balance"); double interest = rs.getDouble("interest"); String details = rs.getString("details"); String name = rs.getString("name"); ba = new BankAccount(bankNr, sortCode, accountNumber, balance, interest, details, name); } rs.close(); }catch(SQLException se){ printSQLException(se); } return ba; } private void printSQLException(SQLException se){ while(se != null){ System.out.print("SQLException: State: " + se.getSQLState()); System.out.println("Severity: " + se.getErrorCode()); System.out.println(se.getMessage()); se = se.getNextException(); } } } </code></pre> <p>I have changed the <strong>getMaxBankNr()</strong> getter as follows:</p> <pre><code>public int getMaxBankNr(){ try{ Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery("SELECT MAX(bankNr) FROM accounts.bankaccounts"); if(rs.next()){ maxBankNr = rs.getInt(1); } }catch(SQLException e){ printSQLException(e); } return(this.maxBankNr); } </code></pre> <p>When <strong>this.maxBankNr = bankAccountDAO.getMaxBankNr()</strong> was called, it wasn't returning an updated <strong>maxBankNr.</strong> This required a new SQL statement to return the proper value.</p> <p>Anyone using a database with a list in the same way as me (i noticed quite a few people with the same problem as me while googling) should make sure that the for loop <strong>really</strong> knows how many times to loop.</p> <p>I would have posted this as an answer, but I can't answer my own question for 8 hours, because I don't have enough points.</p>

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