Vedi la versione AWT.
import java.awt.*; import java.awt.event.*; import javax.swing.*; class JMMTM extends JFrame implements ActionListener { private JTextField txt1, txt2, txt3, txt4; private JLabel lOut; private JButton bMIN, bMAX, bTOT, bMED; public JMMTM() { JPanel pNORTH=new JPanel(); txt1=new JTextField("-20", 10); pNORTH.add(txt1); txt2=new JTextField("-1" , 10); pNORTH.add(txt2); txt3=new JTextField("+1" , 10); pNORTH.add(txt3); txt4=new JTextField("+20", 10); pNORTH.add(txt4); this.add(pNORTH, BorderLayout.NORTH); lOut =new JLabel("???", JLabel.CENTER); this.add(lOut, BorderLayout.CENTER); JPanel pSOUTH=new JPanel(); bMIN=new JButton("Minimo"); bMIN.addActionListener(this); pSOUTH.add(bMIN); bMAX=new JButton("Massimo"); bMAX.addActionListener(this); pSOUTH.add(bMAX); bTOT=new JButton("Totale"); bTOT.addActionListener(this); pSOUTH.add(bTOT); bMED=new JButton("Media"); bMED.addActionListener(this); pSOUTH.add(bMED); this.add(pSOUTH, BorderLayout.SOUTH); this.setTitle("Calcolo minimo/massimo/totale/media"); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.pack(); this.setVisible(true); } public void actionPerformed(ActionEvent evento) { JButton comando=(JButton)evento.getSource(); String msg =new String(); try { double in1=Double.parseDouble(txt1.getText()); double in2=Double.parseDouble(txt2.getText()); double in3=Double.parseDouble(txt3.getText()); double in4=Double.parseDouble(txt4.getText()); double risultato=0; if(comando==bMIN) { risultato=Math.min(Math.min(in1, in2), Math.min(in3, in4)); msg="Minimo = " + risultato; } else if(comando==bMAX) { risultato=Math.max(Math.max(in1, in2), Math.max(in3, in4)); msg="Massimo = " + risultato; } else if(comando==bTOT) { risultato=in1+in2+in3+in4; msg="Totale = "+risultato; } else if(comando==bMED) { risultato=(in1+in2+in3+in4)/4.0; msg="Media = "+risultato; } } catch(Exception eccezione) { msg="??? Input errato ???"; } lOut.setText(msg); } public static void main(String[] args) { JMMTM jFrame = new JMMTM(); } }
Osserva
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JLabel, JButton, JTextField, JPanel, JFrame
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this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);