Eis o meu código em Java: /* To change this license header, choose License Headers in Project Properties. To change this template file, choose Tools | Templates and open the template in the editor. */ package mapaca…

Fiz isso e dá certo. O problema é que estou trabalhando com uma calculadora, então, quando digito o número 1 por exemplo e o mais, aparece o zero no fundo da tela antes de digitar o segundo número. Gostaria de deixar a tela em branco, mas não consigo. Este é o problema. Grato pela resposta.

JENEVES: quando digito o número 1 por exemplo e o mais, aparece o zero no fundo da tela antes de digitar o segundo número Quando o número do display for 0 e você digitar algum número, você ignora o 0 e assume somente o número digitado.

Ajuda para dois problemas em calculadora em java

Eis o meu código em Java:
/*

To change this license header, choose License Headers in Project Properties.
To change this template file, choose Tools | Templates
and open the template in the editor.
*/
package mapacalculadora;

import java.text.DecimalFormat;

/**
*

@author Usuario
*/
public class Calculadora extends javax.swing.JFrame {

/**

Creates new form Calculadora
*/
double num1 = 0, num2 = 0, subtotal = 0, total = 0;
char operacao = ‘_’;
String botao;

public Calculadora() {

initComponents();

}

/**

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”)

// 

private void initComponents() {

visor = new javax.swing.JTextField();

botao7 = new javax.swing.JButton();

botao8 = new javax.swing.JButton();

botao9 = new javax.swing.JButton();

botaodivisao = new javax.swing.JButton();

botao4 = new javax.swing.JButton();

botao5 = new javax.swing.JButton();

botao6 = new javax.swing.JButton();

botaomult = new javax.swing.JButton();

botao1 = new javax.swing.JButton();

botao2 = new javax.swing.JButton();

botao3 = new javax.swing.JButton();

botaosubt = new javax.swing.JButton();

botaoCE = new javax.swing.JButton();

botao0 = new javax.swing.JButton();

botaoigual = new javax.swing.JButton();

botaoadicao = new javax.swing.JButton();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

visor.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

visor.setHorizontalAlignment(javax.swing.JTextField.RIGHT);

visor.setText(“0”);

botao7.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao7.setText(“7”);

botao7.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao7ActionPerformed(evt);

}

});

botao8.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao8.setText(“8”);

botao8.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao8ActionPerformed(evt);

}

});

botao9.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao9.setText(“9”);

botao9.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao9ActionPerformed(evt);

}

});

botaodivisao.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botaodivisao.setText("/");

botaodivisao.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botaodivisaoActionPerformed(evt);

}

});

botao4.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao4.setText(“4”);

botao4.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao4ActionPerformed(evt);

}

});

botao5.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao5.setText(“5”);

botao5.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao5ActionPerformed(evt);

}

});

botao6.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao6.setText(“6”);

botao6.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao6ActionPerformed(evt);

}

});

botaomult.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botaomult.setText("*");

botaomult.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botaomultActionPerformed(evt);

}

});

botao1.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao1.setText(“1”);

botao1.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao1ActionPerformed(evt);

}

});

botao2.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao2.setText(“2”);

botao2.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao2ActionPerformed(evt);

}

});

botao3.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao3.setText(“3”);

botao3.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao3ActionPerformed(evt);

}

});

botaosubt.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botaosubt.setText("-");

botaosubt.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botaosubtActionPerformed(evt);

}

});

botaoCE.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botaoCE.setText(“CE”);

botaoCE.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botaoCEActionPerformed(evt);

}

});

botao0.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botao0.setText(“0”);

botao0.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botao0ActionPerformed(evt);

}

});

botaoigual.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botaoigual.setText("=");

botaoigual.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botaoigualActionPerformed(evt);

}

});

botaoadicao.setFont(new java.awt.Font(“Tahoma”, 0, 36)); // NOI18N

botaoadicao.setText("+");

botaoadicao.addActionListener(new java.awt.event.ActionListener() {

public void actionPerformed(java.awt.event.ActionEvent evt) {

botaoadicaoActionPerformed(evt);

}

});

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());

getContentPane().setLayout(layout);

layout.setHorizontalGroup(

layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addGroup(layout.createSequentialGroup()

.addContainerGap()

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(visor)

.addGroup(layout.createSequentialGroup()

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botao4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao7, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botaoCE, javax.swing.GroupLayout.DEFAULT_SIZE, 92, Short.MAX_VALUE))

.addGap(58, 58, 58)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addGroup(layout.createSequentialGroup()

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botao2, javax.swing.GroupLayout.DEFAULT_SIZE, 94, Short.MAX_VALUE)

.addComponent(botao0, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))

.addGap(59, 59, 59)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)

.addComponent(botao3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botaoigual, javax.swing.GroupLayout.DEFAULT_SIZE, 97, Short.MAX_VALUE)))

.addGroup(layout.createSequentialGroup()

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botao8, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao5, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))

.addGap(59, 59, 59)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botao6, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao9, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))))

.addGap(54, 54, 54)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botaosubt, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botaomult, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botaodivisao, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botaoadicao, javax.swing.GroupLayout.DEFAULT_SIZE, 91, Short.MAX_VALUE))))

.addContainerGap())

);

layout.setVerticalGroup(

layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addGroup(layout.createSequentialGroup()

.addContainerGap()

.addComponent(visor, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)

.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botaodivisao, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)

.addComponent(botao7, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao8, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao9, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))

.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)

.addComponent(botaomult, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao6, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao5, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))

.addGap(15, 15, 15)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botao1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)

.addComponent(botaosubt, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))

.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(botaoCE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)

.addComponent(botaoadicao, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botaoigual, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

.addComponent(botao0, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))

.addContainerGap())

);

pack();
}//

public void digitarNumeros(String temp1){

String temp = visor.getText();

if (temp==“0”){

visor.setText(temp1);

}else{

double total;

total = (Double.parseDouble(temp) * 10) + Double.parseDouble(temp1);

DecimalFormat df = new DecimalFormat("#.########");

visor.setText(df.format(total));

}

}

private void botao1ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“1”);

}

private void botao2ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“2”);

}

private void botao3ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“3”);

}

private void botao4ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“4”);

}

private void botao5ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“5”);

}

private void botao6ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“6”);

}

private void botao7ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“7”);

}

private void botao8ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“8”);

}

private void botao9ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“9”);

}

private void botao0ActionPerformed(java.awt.event.ActionEvent evt) {

digitarNumeros(“0”);

}

private void botaoCEActionPerformed(java.awt.event.ActionEvent evt) {

visor.setText(“0”);

}

private void botaoadicaoActionPerformed(java.awt.event.ActionEvent evt) {

// TODO add your handling code here:

operacao = ‘+’;

num1 = Double.valueOf(visor.getText());

visor.setText(“0”);

}

private void botaosubtActionPerformed(java.awt.event.ActionEvent evt) {

// TODO add your handling code here:

operacao = ‘-’;

num1 = Double.valueOf(visor.getText());

visor.setText(“0”);

}

private void botaomultActionPerformed(java.awt.event.ActionEvent evt) {

// TODO add your handling code here:

operacao = ‘*’;

num1 = Double.valueOf(visor.getText());

visor.setText(“0”);

}

private void botaodivisaoActionPerformed(java.awt.event.ActionEvent evt) {

// TODO add your handling code here:

operacao = ‘/’;

num1 = Double.valueOf(visor.getText());

visor.setText(“0”);

}

private void botaoigualActionPerformed(java.awt.event.ActionEvent evt) {

// TODO add your handling code here:

num2 = Double.valueOf(visor.getText());

if (operacao != ‘<em>’){

switch(operacao){

case ‘+’:

total = num1 + num2;

visor.setText((String.valueOf(total)));

num1 = 0;

num2 = 0;

total = 0;

operacao = '</em>’;

break;

case ‘-’:

total = num1 - num2;

visor.setText((String.valueOf(total)));

break;

case ‘*’:

total = num1 * num2;

visor.setText((String.valueOf(total)));

break;

case ‘/’:

total = num1 / num2;

visor.setText((String.valueOf(total)));

break;

default:

visor.setText(“Operação incorreta”);

break;

}
 }

}

/**

@param args the command line arguments
/
public static void main(String args[]) {
/ Set the Nimbus look and feel /
//
/ If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
- For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
  */
  try {
  for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
  if (“Nimbus”.equals(info.getName())) {
  javax.swing.UIManager.setLookAndFeel(info.getClassName());
  break;
  }
  }
  } catch (ClassNotFoundException ex) {
  java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
  } catch (InstantiationException ex) {
  java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
  } catch (IllegalAccessException ex) {
  java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
  } catch (javax.swing.UnsupportedLookAndFeelException ex) {
  java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
  }
  //
```
/* Create and display the form */

java.awt.EventQueue.invokeLater(new Runnable() {

public void run() {

new Calculadora().setVisible(true);

}

});

}
```

// Variables declaration - do not modify

private javax.swing.JButton botao0;

private javax.swing.JButton botao1;

private javax.swing.JButton botao2;

private javax.swing.JButton botao3;

private javax.swing.JButton botao4;

private javax.swing.JButton botao5;

private javax.swing.JButton botao6;

private javax.swing.JButton botao7;

private javax.swing.JButton botao8;

private javax.swing.JButton botao9;

private javax.swing.JButton botaoCE;

private javax.swing.JButton botaoadicao;

private javax.swing.JButton botaodivisao;

private javax.swing.JButton botaoigual;

private javax.swing.JButton botaomult;

private javax.swing.JButton botaosubt;

private javax.swing.JTextField visor;

// End of variables declaration

}

O problema é que ao fazer a soma de dois numeros, na troca de tela, só posso colocar o zero após o primeiro número. Sei que o comando para limpar o campo de texto seria visor.setText(""), mas não consigo implementar, pois por exigência do meu professor tive que trabalhar com variáveis numéricas para concatenar e aí se erro o comando para limpar, aparece o seguinte erro: Exception in thread “AWT-EventQueue-0” java.lang.NumberFormatException: empty String.
Gostaria de saber se há algum meio para contornar este problema.
Outra dificuldade é que que acontece o seguinte:
Por exemplo, digamos que vou somar 2+2 e depois 5 + 4. Quando digito 2 + 2 =, aparece o resultado correto que é 4.0, mas quando tento começar uma nova operação, ao invés do visor limpar, o 5 da operação seguinte é concatenado com o 4, formando um 45. Preciso de ajuda neste item também. Preciso de ajuda urgente, pois não tenho muito tempo para resolver este problema. Grato por qualquer ajuda.

4 Respostas

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