Pessoal, alguém pode me ajudar com este erro, olha a classe e o erro abaixo:
CLASSE:
[code]package br.iterator.semPadrao;
import java.util.ArrayList;
import javax.swing.JOptionPane;
/**
*
-
@author Vagner Duarte
*/
public class MostraCadastro extends javax.swing.JFrame {/** Creates new form MostraCadastro */
public MostraCadastro() {
initComponents();
}public void arraylistcadastro(){
CadastroAluno cadastro = new CadastroAluno();ArrayList alunos = cadastro.lista_alunos();
if(alunos.size() <= 0){
JOptionPane.showMessageDialog(null, “A lista esta vazia”);
}for(int i =0; i <= alunos.size();i++){
Aluno aluno = (Aluno) alunos.get(i);
jta_cadastro.append(aluno.getNome());
jta_cadastro.append(aluno.getSobrenome());
jta_cadastro.append(aluno.getTel());
jta_cadastro.append(aluno.getCpf());
}}
/** 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”)
//
private void initComponents() {jLabel1 = new javax.swing.JLabel();
jScrollPane1 = new javax.swing.JScrollPane();
jta_cadastro = new javax.swing.JTextArea();setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setFont(new java.awt.Font(“Tahoma”, 1, 14)); // NOI18N
jLabel1.setForeground(java.awt.Color.blue);
jLabel1.setText(“Alunos Cadastrados:”);jta_cadastro.setColumns(20);
jta_cadastro.setRows(5);
jScrollPane1.setViewportView(jta_cadastro);javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(131, 131, 131)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addGap(20, 20, 20)
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 346, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap(34, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(33, 33, 33)
.addComponent(jLabel1)
.addGap(18, 18, 18)
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 152, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(80, Short.MAX_VALUE))
);pack();
}//
/**
-
@param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MostraCadastro().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextArea jta_cadastro;
// End of variables declaration -
}[/code]
ERRO:
run:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at br.iterator.semPadrao.MostraCadastro.arraylistcadastro(MostraCadastro.java:32)
at br.iterator.semPadrao.IteratorGui.bt_cadastroActionPerformed(IteratorGui.java:222)
at br.iterator.semPadrao.IteratorGui.access$500(IteratorGui.java:20)
at br.iterator.semPadrao.IteratorGui$6.actionPerformed(IteratorGui.java:112)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6216)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
at java.awt.Component.processEvent(Component.java:5981)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4583)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4556)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4220)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4150)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2475)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)