Есть два текстовых поля и две кнопки. Нужно, чтобы при нажатии клавиши Enter при фокусе ввода в любом текстовом поле срабатывала первая кнопка.

getRootPane().setDefaultButton(btnOK);

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package maintask;
 
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.KeyStroke;
 
/**
 *
 * @author Animator404n
 */
public class NewJFrame extends javax.swing.JFrame {
 
    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() {
        initComponents();
        
        Action act = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Yes");
            }
        };
        Button1.addActionListener(act);
        getRootPane().setDefaultButton(Button1);
    }
 
    /**
     * 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() {
 
        jPanel1 = new javax.swing.JPanel();
        Button1 = new javax.swing.JButton();
        Button2 = new javax.swing.JButton();
        TextField1 = new javax.swing.JTextField();
        TextField2 = new javax.swing.JTextField();
 
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
 
        Button1.setText("Button 1");
 
        Button2.setText("Button 2");
 
        TextField1.setColumns(10);
        TextField1.setToolTipText("");
        TextField1.setColumns(15);
        TextField1.setCursor(new java.awt.Cursor(java.awt.Cursor.SW_RESIZE_CURSOR));
        TextField1.setHighlighter(null);
 
        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                    .addComponent(TextField2)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addComponent(Button1)
                        .addGap(18, 18, 18)
                        .addComponent(Button2))
                    .addComponent(TextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 168, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap())
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(TextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addComponent(TextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(Button1)
                    .addComponent(Button2))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
 
        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()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        );
 
        pack();
    }// </editor-fold>                        
  public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see [url]http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html[/url] 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Windows".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
 
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }
    /**
     * @param args the command line arguments
     */
   
    // Variables declaration - do not modify                     
    private javax.swing.JButton Button1;
    private javax.swing.JButton Button2;
    private javax.swing.JTextField TextField1;
    private javax.swing.JTextField TextField2;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                   
}