Calculadora

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.HashSet;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingConstants;

public class Calculadora extends JFrame implements ActionListener{
    JButton btnSoma, btnDiferenca, btnMult, btnDivide, btnClear;
    JLabel txt1, txt2, txt3;
    JTextField txtValor1, txtValor2, txtResul;
    public void actionPerformed (ActionEvent e){
        float num1, num2, resul;
        try{
            num1 = Float.parseFloat (txtValor1.getText());
            num2 = Float.parseFloat (txtValor2.getText());
        }catch (NumberFormatException erro){
            num1=0;
            num2=0;
        }
        if (e.getSource() == btnSoma){
            resul = num1+num2;
            txtResul.setText(String.format("%5.2f", resul));
        }
        else if (e.getSource()==btnDiferenca){
            resul = num1-num2;
            txtResul.setText(String.format("%5.2f", resul));
        }
        else if (e.getSource()== btnDivide){
            resul = num1 / num2;
            txtResul.setText (String.format("%5.2f", resul));
        }
        else if (e.getSource() == btnMult){
            resul = num1 * num2;
            txtResul.setText (String.format("%5.2f", resul));
        }
        else{
            txtValor1.setText("");
            txtValor2.setText("");
            txtResul.setText("");
        }

    }


public Calculadora(){
    setLayout (new BorderLayout());
    btnSoma = new JButton ("+");
    btnDiferenca = new JButton ("-");
    btnDivide = new JButton ("/");
    btnMult = new JButton ("x");
    btnClear = new JButton ("Clear");
    JPanel leste = new JPanel (new GridLayout (5,1));
    leste.add(btnSoma);
    leste.add(btnDiferenca);
    leste.add(btnDivide);
    leste.add(btnMult);
    leste.add(btnClear);
    add (leste, BorderLayout.EAST);
    JPanel centro = new JPanel (new GridLayout (3,2));
    txt1 = new JLabel ("Entre com o valor 1   :", SwingConstants.RIGHT);
    txt2 = new JLabel ("Entre com o valor 2   :", SwingConstants.RIGHT);
    txt3 = new JLabel ("Resultado   :", SwingConstants.RIGHT);
    txtValor1 = new JTextField (5);
    txtValor2 = new JTextField (5);
    txtResul = new JTextField (5);
    centro.add (txt1);
    centro.add (txtValor1);
    centro.add (txt2);
    centro.add (txtValor2);
    centro.add (txt3);
    centro.add (txtResul);
    add (centro, BorderLayout.CENTER);
    btnSoma.addActionListener(this);
    btnDiferenca.addActionListener(this);
    btnMult.addActionListener(this);
    btnDivide.addActionListener(this);
    btnClear.addActionListener(this);
}

public static void main (String [] args){
    Calculadora tela = new Calculadora ();
    tela.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    tela.setSize (350,250);
    tela.setLocation (500,300);
    tela.setVisible(true);
}

}