Problema com JButton (Action performed)

Onde você está chamando o método botaoActionPerformed?
Posta o código completo da tela.

Código gerado pela IDE do Netbeans:

/*

• 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 apsj;

import javax.swing.JOptionPane;

/**
*

• @author AlucardHell
  */
  public class Painel extends javax.swing.JPanel {

  /**

  • Creates new form Painel
    */
    public Painel() {
    initComponents();
    }

  /**

  • 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() {
    

    jScrollPane1 = new javax.swing.JScrollPane();
    
    textoarea = new javax.swing.JTextArea();
    
    botao = new javax.swing.JButton();
    

    textoarea.setColumns(20);
    
    textoarea.setFont(new java.awt.Font(“Serif”, 0, 18)); // NOI18N
    
    textoarea.setRows(5);
    
    textoarea.setToolTipText("");
    
    jScrollPane1.setViewportView(textoarea);
    

    botao.setText(“jButton1”);
    
    botao.addActionListener(new java.awt.event.ActionListener() {
    
    public void actionPerformed(java.awt.event.ActionEvent evt) {
    
    botaoActionPerformed(evt);
    
    }
    
    });
    

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    
    this.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(115, 115, 115)
    
    .addComponent(botao, javax.swing.GroupLayout.PREFERRED_SIZE, 247, javax.swing.GroupLayout.PREFERRED_SIZE))
    
    .addGroup(layout.createSequentialGroup()
    
    .addGap(33, 33, 33)
    
    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 588, javax.swing.GroupLayout.PREFERRED_SIZE)))
    
    .addContainerGap(51, Short.MAX_VALUE))
    
    );
    
    layout.setVerticalGroup(
    
    layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
    
    .addGroup(layout.createSequentialGroup()
    
    .addContainerGap()
    
    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 117, javax.swing.GroupLayout.PREFERRED_SIZE)
    
    .addGap(51, 51, 51)
    
    .addComponent(botao, javax.swing.GroupLayout.PREFERRED_SIZE, 69, javax.swing.GroupLayout.PREFERRED_SIZE)
    
    .addContainerGap(52, Short.MAX_VALUE))
    
    );
    
    }//
    

  private void botaoActionPerformed(java.awt.event.ActionEvent evt) {

  JOptionPane.showMessageDialog(null, "Olá Mundo");
  

  }

  // Variables declaration - do not modify
  
  private javax.swing.JButton botao;
  
  private javax.swing.JScrollPane jScrollPane1;
  
  private javax.swing.JTextArea textoarea;
  
  // End of variables declaration
  
  }