Si in effetti
Allora in questa parte di codice creo il panel chiamato SouthPanel con i JButton

import java.awt.*;
import javax.swing.*;
import javax.swing.border.LineBorder;

public class SouthPanel extends JComponent{

JTextField Numlev;
JTextField Numgate;
JTextField Input;
JTextField Output;
JLabel Jlbl1;
JLabel Jlbl2;
JLabel Jlbl3;
JLabel Jlbl4;
JButton Jbut1;
JButton Jbut2;
JButton Jbut3;
JButton Jbut4;



public SouthPanel(){

this.setLayout(null);

//Prima Etichetta
Jlbl1 = new JLabel("Numero di Input");
Jlbl1.setSize(100,30);
Jlbl1.setLocation(10,15);
Jlbl1.setLabelFor(Input);
Input = new JTextField();
Input.setDocument(new NumberDocument());
Input.addKeyListener(new KeyHandlerOnlyNum());
Input.setSize(50,20);
Input.setLocation(120,20);
Input.setEditable(false);
Input.setBackground(Color.white);
Input.setText("0");

//Seconda Etichetta
Jlbl2 = new JLabel("Numero di Output");
Jlbl2.setSize(100,30);
Jlbl2.setLocation(180,15);
Jlbl2.setLabelFor(Output);
Output = new JTextField();
Output.setDocument(new NumberDocument());
Output.addKeyListener(new KeyHandlerOnlyNum());
Output.setSize(50,20);
Output.setLocation(290,20);
Output.setEditable(false);
Output.setBackground(Color.white);
Output.setText("0");

//Terza Etichetta
Jlbl3 = new JLabel("Numero di Porte");
Jlbl3.setSize(100,30);
Jlbl3.setLocation(350,15);
Jlbl3.setLabelFor(Numlev);
Numlev = new JTextField();
Numlev.setDocument(new NumberDocument());
Numlev.addKeyListener(new KeyHandlerOnlyNum());
Numlev.setSize(50,20);
Numlev.setLocation(460,20);
Numlev.setEditable(false);
Numlev.setBackground(Color.white);
Numlev.setText("0");

//Quarta Etichetta
Jlbl4 = new JLabel("Numero di Livelli");
Jlbl4.setSize(100,30);
Jlbl4.setLocation(520,15);
Jlbl4.setLabelFor(Numgate);
Numgate = new JTextField();
Numgate.setDocument(new NumberDocument());
Numgate.addKeyListener(new KeyHandlerOnlyNum());
Numgate.setSize(50,20);
Numgate.setLocation(630,20);
Numgate.setEditable(false);
Numgate.setBackground(Color.white);
Numgate.setText("0");

Jbut1 = new JButton();
Jbut1.setSize(16,16);
Jbut1.setLocation(127,50);
Jbut1.setBackground(new Color(238,238,238));
Jbut1.setBorder(new LineBorder(Color.LIGHT_GRAY));
Jbut1.setIcon(new ImageIcon("img/minus.gif"));

Jbut2 = new JButton();
Jbut2.setSize(16,16);
Jbut2.setLocation(147,50);
Jbut2.setBackground(new Color(238,238,238));
Jbut2.setBorder(new LineBorder(Color.LIGHT_GRAY));
Jbut2.setIcon(new ImageIcon("img/plus.gif"));



Jbut3 = new JButton();
Jbut3.setSize(16,16);
Jbut3.setLocation(297,50);
Jbut3.setBackground(new Color(238,238,238));
Jbut3.setBorder(new LineBorder(Color.LIGHT_GRAY));
Jbut3.setIcon(new ImageIcon("img/minus.gif"));

Jbut4 = new JButton();
Jbut4.setSize(16,16);
Jbut4.setLocation(317,50);
Jbut4.setBackground(new Color(238,238,238));
Jbut4.setBorder(new LineBorder(Color.LIGHT_GRAY));
Jbut4.setIcon(new ImageIcon("img/plus.gif"));

this.add(Numlev);
this.add(Jlbl1);
this.add(Numgate);
this.add(Jlbl2);
this.add(Input);
this.add(Jlbl3);
this.add(Output);
this.add(Jlbl4);
this.add(Jbut1);
this.add(Jbut2);
this.add(Jbut3);
this.add(Jbut4);


this.setVisible(true);
}
}

e qui la parte dove creo le action all'interno della classe GUI

protected void createActions() {
decInput = new AbstractAction("Decrementa Input"){
@Override
public void actionPerformed(ActionEvent e){
if(Integer.parseInt(Split.SP.Input.getText())>0)
Split.SP.Input.setText((Integer.parseInt(Split.SP. Input.getText())-1)+"");
}
};

incInput = new AbstractAction("Incrementa Input"){
@Override
public void actionPerformed(ActionEvent e){
Split.SP.Input.setText((Integer.parseInt(Split.SP. Input.getText())+1)+"");
}
};

decOutput = new AbstractAction("Decrementa Ouput"){
@Override
public void actionPerformed(ActionEvent e){
if(Integer.parseInt(Split.SP.Output.getText())>0)
Split.SP.Output.setText((Integer.parseInt(Split.SP .Output.getText())-1)+"");
}
};

incOutput = new AbstractAction("Incrementa Output"){
@Override
public void actionPerformed(ActionEvent e){
Split.SP.Output.setText((Integer.parseInt(Split.SP .Output.getText())+1)+"");
}
};
}

infine qui dove le assegno, sempre all'interno della classe GUI

protected void setAction(){
Split.SP.Jbut1.setAction(decInput);
Split.SP.Jbut2.setAction(incInput);
Split.SP.Jbut3.setAction(decOutput);
Split.SP.Jbut4.setAction(incOutput);
}

a te la magiaXD