Salve,
ho questa semplicissima applicazione:
consiste in un JPanel che contiene una jTextArea (contenuta a sua volta in un JScrollPane) e due jButton con etichetta "Chiudi" e "Vai", il primo chiude l'applicazione mentre su "Vai" ho definito un evento actionPerformed, per cui alla pressione di esso eseguo queste semplici istruzioni:
codice:
int index = 0;
jTextArea1.setText("");
while (index<1000) {
index++;
jTextArea1.append("Passo "+index+"\n");
scriviFile();
}
mentre scriviFile(); è un metodo che provvede a scrivere 1000 volte (ovviamente è per una prova) un file.

Il problema è che il contenuto di jTextArea1 NON viene aggiornato ad ogni iterazione del ciclo, ma dopo che è stato scritto 1000 volte il file, ossia dopo l'ultima iterazione :master:


Posto per maggior chiarezza l'intero codice

Grazie

codice:
package tools;

import java.io.*;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.String;

public class ProvaLog extends javax.swing.JFrame {
    
    public ProvaLog() {
        initComponents();
    }
    
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">//GEN-BEGIN:initComponents
    private void initComponents() {
        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();
        jButton2 = new javax.swing.JButton();
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Prova Finestra di Log");
        jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder(null, "Prova Log", javax.swing.border.TitledBorder.DEFAULT_JUSTIFICATION, javax.swing.border.TitledBorder.DEFAULT_POSITION, new java.awt.Font("Tahoma", 1, 12)));
        jScrollPane1.setHorizontalScrollBarPolicy(javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
        jScrollPane1.setVerticalScrollBarPolicy(javax.swing.ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        jTextArea1.setColumns(30);
        jTextArea1.setFont(new java.awt.Font("Monospaced", 0, 13));
        jTextArea1.setRows(5);
        jScrollPane1.setViewportView(jTextArea1);

        jButton2.setText("Vai");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });

        org.jdesktop.layout.GroupLayout jPanel1Layout = new org.jdesktop.layout.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .add(jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED, 38, Short.MAX_VALUE)
                .add(jButton2)
                .addContainerGap())
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.TRAILING)
                    .add(jButton2)
                    .add(jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        jButton1.setText("Chiudi");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(jPanel1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .add(jButton1))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .add(jButton1)
                .addContainerGap())
        );
        pack();
    }// </editor-fold>//GEN-END:initComponents
    
    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton2ActionPerformed
        vai();
    }//GEN-LAST:event_jButton2ActionPerformed
    
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed
        System.exit(0);
    }//GEN-LAST:event_jButton1ActionPerformed
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new ProvaLog().setVisible(true);
            }
        });
    }
    
    private void vai() {
        int index = 0;
        jTextArea1.setText("");
        while (index<1000) {
            index++;
            jTextArea1.append("Passo "+index+"\n");
            scriviFile();
        }
    }
    
    private void scriviFile() {
        File descrizioni;
        String testo;
        int err;
        String filename_input = "";        
        
        filename_input = "C://prova_log___.txt";       
        descrizioni = new File(filename_input);
        if (!descrizioni.exists()) {
            try {
                descrizioni.createNewFile();
            } catch (IOException e) {
                System.out.println("Unable to create "+filename_input+": "+e.getMessage());
            }
        }        
        testo = "Questo è un file di testo utilizzato per una prova.";        
        try {
            scriviFile(descrizioni, testo);
        } catch (FileNotFoundException ex2) {
            System.out.println(ex2.getMessage());
        } catch (IOException ex2) {
            System.out.println(ex2.getMessage());
        }               
    }

        
    void scriviFile(File unFile, String testo) throws
            FileNotFoundException, IOException {
        if (unFile == null) {
            throw new IllegalArgumentException("File should not be null.");
        }
        if (!unFile.exists()) {
            throw new FileNotFoundException("File does not exist: " + unFile);
        }
        if (!unFile.isFile()) {
            throw new IllegalArgumentException("Should not be a directory: " + unFile);
        }
        if (!unFile.canWrite()) {
            throw new IllegalArgumentException("File cannot be written: " + unFile);
        }
        
        Writer output = null;
        try {
            output = new BufferedWriter(new FileWriter(unFile));
            output.write(testo);
        } finally {
            if (output != null) {
                output.close();
            }
        }
        System.out.println("File creato...");
    }
    
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration//GEN-END:variables
}