Passando dados de um combobox para list ou table - JAVA

Estou fazendo uma espécie de programa contábil para um projeto da escola(curso técnico integrado ao médio) e preciso de ajuda com um pequeno detalhe:

Como tentei exemplificar na imagem quero passar o dado selecionado no combobox para outro campo(list ou table, de preferencia) ao clicar no botão. Após alguns testes cheguei perto usando o jlist, mas o problema é que o bendito está substituindo ao invés de acrescentar.
Segue código:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package view;

import java.awt.Component;
import java.text.ParseException;
import javax.swing.ImageIcon;
import java.util.ArrayList;
import javax.swing.DefaultComboBoxModel;
import javax.swing.DefaultListModel;
import javax.swing.JFormattedTextField;
import javax.swing.JOptionPane;
import javax.swing.text.MaskFormatter;

/**
 *
 * @author Controle
 */
public class FormContas extends javax.swing.JInternalFrame {

    /**
     * Creates new form FormLanchonete
     */
    public String nomes;

    public FormContas() {
        initComponents();
        setFrameIcon(new ImageIcon(this.getClass().getResource("../imagem/acco16.png")));
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        buttonGroup1 = new javax.swing.ButtonGroup();
        jPanel2 = new javax.swing.JPanel();
        combo = new javax.swing.JComboBox<>();
        botaopagar = new javax.swing.JButton();
        jPanel3 = new javax.swing.JPanel();
        txtnome = new javax.swing.JTextField();
        txtvalor = new javax.swing.JTextField();
        txtdia = new javax.swing.JTextField();
        txtmes = new javax.swing.JTextField();
        botao = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jScrollPane2 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();

        setBackground(new java.awt.Color(26, 147, 220));
        setClosable(true);
        setMaximizable(true);
        setTitle("Contas");

        jPanel2.setBorder(javax.swing.BorderFactory.createTitledBorder("Contas a Pagar"));

        combo.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                comboActionPerformed(evt);
            }
        });

        botaopagar.setText("Pagar");
        botaopagar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                botaopagarActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(combo, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(botaopagar))
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(combo, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(botaopagar))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        jPanel3.setBorder(javax.swing.BorderFactory.createTitledBorder("Cadastro de Conta"));

        txtnome.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                txtnomeActionPerformed(evt);
            }
        });

        txtvalor.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                txtvalorActionPerformed(evt);
            }
        });

        txtdia.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                txtdiaActionPerformed(evt);
            }
        });

        txtmes.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                txtmesActionPerformed(evt);
            }
        });

        botao.setText("Enviar");
        botao.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                botaoActionPerformed(evt);
            }
        });

        jLabel1.setText("Nome");

        jLabel2.setText("Valor");

        jLabel3.setText("Dia do vencimento");

        jLabel4.setText("Mês do vencimento");

        javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
        jPanel3.setLayout(jPanel3Layout);
        jPanel3Layout.setHorizontalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel3Layout.createSequentialGroup()
                .addGap(22, 22, 22)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(txtnome, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel1))
                .addGap(18, 18, 18)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(txtvalor, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel2))
                .addGap(18, 18, 18)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(txtdia, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel3))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel3Layout.createSequentialGroup()
                        .addComponent(jLabel4)
                        .addGap(0, 0, Short.MAX_VALUE))
                    .addGroup(jPanel3Layout.createSequentialGroup()
                        .addComponent(txtmes, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 16, Short.MAX_VALUE)
                        .addComponent(botao)))
                .addContainerGap())
        );
        jPanel3Layout.setVerticalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel3Layout.createSequentialGroup()
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(jLabel2)
                    .addComponent(jLabel3)
                    .addComponent(jLabel4))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(txtnome, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(txtvalor, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(txtdia, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(txtmes, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(botao))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        MaskFormatter mascaraCampo = null;
        try {
            mascaraCampo = new MaskFormatter("#.###,##");
        } catch (ParseException e) {
        }
        JFormattedTextField campoFormatado = new JFormattedTextField(mascaraCampo);

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {},
                {},
                {},
                {}
            },
            new String [] {

            }
        ));
        jScrollPane2.setViewportView(jTable1);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jScrollPane2)
                    .addComponent(jPanel3, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jPanel2, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(10, 10, 10)
                .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 105, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(526, Short.MAX_VALUE))
        );

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

    private void txtnomeActionPerformed(java.awt.event.ActionEvent evt) {                                        
        // TODO add your handling code here:


    }                                       

    private void txtvalorActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:

    }                                        

    private void txtdiaActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:

    }                                      

    private void txtmesActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:

    }                                      

    private void botaoActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        String nome = txtnome.getText();
        String valor = txtvalor.getText();
        String dia = txtdia.getText();
        String mes = txtmes.getText();

        try {
            int dias = Integer.parseInt(dia);
            int meses = Integer.parseInt(mes);

            combo.addItem(nome + " R$" + valor + " Vence:" + dias + "/" + meses);
        } catch (NumberFormatException e) {
            Component frame = null;
            JOptionPane.showMessageDialog(frame, "Número Errado!");
        }
    }                                     

    private void botaopagarActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
        String nome = txtnome.getText();
        String valor = txtvalor.getText();
        String dia = txtdia.getText();
        String mes = txtmes.getText();
        
        
        try {
            int dias = Integer.parseInt(dia);
            int meses = Integer.parseInt(mes);

            
            ((DefaultComboBoxModel) combo.getModel()).removeElementAt(combo.getSelectedIndex());
        } catch (NumberFormatException e) {
            Component frame = null;
            JOptionPane.showMessageDialog(frame, "Número Errado!");
        }
    }                                          

    private void comboActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
    }                                     


    // Variables declaration - do not modify                     
    private javax.swing.JButton botao;
    private javax.swing.JButton botaopagar;
    private javax.swing.ButtonGroup buttonGroup1;
    private javax.swing.JComboBox<String> combo;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTable jTable1;
    private javax.swing.JTextField txtdia;
    private javax.swing.JTextField txtmes;
    private javax.swing.JTextField txtnome;
    private javax.swing.JTextField txtvalor;
    // End of variables declaration                   

}

Esquece, consegui resolvê-lo. Deixo minha solução para tentar ajudar pobres almas que poderão ter a mesma dúvida:

Esse no começo da classe:

private DefaultListModel dlm;

Esse no meu caso no FormContas():

dlm=new DefaultListModel();
jList1.setModel(dlm);

e esse no botão:

dlm.addElement(combo.getSelectedItem());