This is my Java code at the moment (using netbeans IDE), I have tried to set th value of cell 4,4 to A in the following code, outputCadence.getModel().setValueAt(items.A[5], 4, 4); , however this does absolutely nothing, I'm a bit of a noob so I'm not sure if I'm missing something obvious, any help greatly apreciated :) (items.A[] is a string array in the items class with a fith element of "D")

public class cadenceGUI extends javax.swing.JFrame {

    public cadenceGUI() {
        initComponents();
    }


    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        keyCombo = keyCombo = new javax.swing.JComboBox(items.keylist);
        jLabel1 = new javax.swing.JLabel();
        jScrollPane1 = new javax.swing.JScrollPane();
        outputCadence = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        keyCombo.setModel(new javax.swing.DefaultComboBoxModel(items.keylist));

        jLabel1.setText("Select a key:");

        outputCadence.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {"Perfect", null, null, null},
                {"Imperfect", null, null, null},
                {"Plagal", null, null, null},
                {"Interrupted", null, null, null}
            },
            new String [] {
                "Cadence", "Starting Chord", "Second Chord", "Finishing Chord"
            }
        ) {
            Class[] types = new Class [] {
                java.lang.String.class, java.lang.String.class, java.lang.String.class, java.lang.String.class
            };
            boolean[] canEdit = new boolean [] {
                false, true, true, true
            };

            public Class getColumnClass(int columnIndex) {
                return types [columnIndex];
            }

            public boolean isCellEditable(int rowIndex, int columnIndex) {
                return canEdit [columnIndex];
            }
        });
        jScrollPane1.setViewportView(outputCadence);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel1)
                    .addComponent(keyCombo, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 375, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(15, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel1)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(keyCombo, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 92, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(194, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>


    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(cadenceGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(cadenceGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(cadenceGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(cadenceGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }

        outputCadence.getModel().setValueAt(items.A[5], 4, 4);

        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new cadenceGUI().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JLabel jLabel1;
    private javax.swing.JScrollPane jScrollPane1;
    private static javax.swing.JComboBox keyCombo;
    public static javax.swing.JTable outputCadence;
    // End of variables declaration
}

That looks like you're setting that cell before you create the GUI, and when you create the GUI you set a new model. Try setting the cell after creating the GUI

  • arrays in Programming languages starting with zero,

  • your JTable has 4 * 4 elements, then setValueAt(whatever, 3, 3) could be last botton cell on left side

  • debug before if items.A[5] returns some value

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