java.lang.ArithmeticException не может понять, почему

Question

Я работаю над калькулятором и использую генератор GUI NetBeans, поэтому он может быть немного неясным и запутанным. (Полный код http://pastebin.com/ZLcM74ZQ, как это было слишком долго)

package rechnerfinal; 

/** 
* 
* @author Fredrik 
*/ 
public class RechnerJFrame extends javax.swing.JFrame { 

    /** 
    * Creates new form RechnerJFrame 
    */ 
    private int value1; 
    private int value2; 
    private int Rechenoperation; 
    public RechnerJFrame() { 
     initComponents(); 
    } 

//Generated Code....      

    private void jButton9ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //7 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(7); 
     } else { 
      labeltextNeu = labeltext + "7"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton7ActionPerformed(java.awt.event.ActionEvent evt) {           
     //÷ 
     value1 = Integer.valueOf(jLabel1.getText()); 
     Rechenoperation = 4; 
     jLabel1.setText("0"); 
    }           

    private void jButton21ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //1 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(1); 
     } else { 
      labeltextNeu = labeltext + "0"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton17ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //1 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(1); 
     } else { 
      labeltextNeu = labeltext + "1"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton10ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //8 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(8); 
     } else { 
      labeltextNeu = labeltext + "8"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton11ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //9 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(9); 
     } else { 
      labeltextNeu = labeltext + "9"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton13ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //4 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(4); 
     } else { 
      labeltextNeu = labeltext + "4"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton14ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //5 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(5); 
     } else { 
      labeltextNeu = labeltext + "5"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton15ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //6 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(6); 
     } else { 
      labeltextNeu = labeltext + "6"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton18ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //2 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(2); 
     } else { 
      labeltextNeu = labeltext + "2"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton19ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
     //3 
     String labeltextNeu = null; 
     String labeltext = jLabel1.getText(); 
     if(labeltext == "0") { 
      setlabeltext(3); 
     } else { 
      labeltextNeu = labeltext + "3"; 
      setlabeltext(Integer.valueOf(labeltextNeu)); 
     } 
    }           

    private void jButton16ActionPerformed(java.awt.event.ActionEvent evt) {           
     //+ 
     value1 = Integer.valueOf(jLabel1.getText()); 
     Rechenoperation = 1; 
     jLabel1.setText("0"); 
    }           

    private void jButton24ActionPerformed(java.awt.event.ActionEvent evt) {           
     //= 
     int Ergebnis; 
     switch(Rechenoperation) { 
      case 1: //+ 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1 + value2; 
       setlabeltext(Ergebnis); 
      case 2: //- 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1 - value2; 
       setlabeltext(Ergebnis); 
      case 3: //x 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1 * value2; 
       setlabeltext(Ergebnis); 
      case 4: //: 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1/value2; 
       setlabeltext(Ergebnis); 
     } 
     Ergebnis = 0; 
    }           

    private void jButton23ActionPerformed(java.awt.event.ActionEvent evt) {           
     //AC 
     jLabel1.setText("0"); 
     value1 = 0; 
     value2 = 0; 
     Rechenoperation = 0; 
    }           

    private void jButton12ActionPerformed(java.awt.event.ActionEvent evt) {           
     //- 
     value1 = Integer.valueOf(jLabel1.getText()); 
     Rechenoperation = 2; 
     jLabel1.setText("0"); 
    }           

    private void jButton8ActionPerformed(java.awt.event.ActionEvent evt) {           
     //* 
     value1 = Integer.valueOf(jLabel1.getText()); 
     Rechenoperation = 3; 
     jLabel1.setText("0"); 
    }           

    private void jButton22ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
    }           

    private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {           
     // TODO add your handling code here: 
    }           


    public void setlabeltext(int labelwert) { 
     jLabel1.setText(Integer.toString(labelwert)); 
    } 
    /** 
    * @param args the command line arguments 
    */ 
    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 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(RechnerJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } catch (InstantiationException ex) { 
      java.util.logging.Logger.getLogger(RechnerJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } catch (IllegalAccessException ex) { 
      java.util.logging.Logger.getLogger(RechnerJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } catch (javax.swing.UnsupportedLookAndFeelException ex) { 
      java.util.logging.Logger.getLogger(RechnerJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); 
     } 
     //</editor-fold> 

     /* Create and display the form */ 
     java.awt.EventQueue.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       new RechnerJFrame().setVisible(true); 
      } 
     }); 
    } 

    // Variables declaration - do not modify      
    private javax.swing.JButton jButton1; 
    private javax.swing.JButton jButton10; 
    private javax.swing.JButton jButton11; 
    private javax.swing.JButton jButton12; 
    private javax.swing.JButton jButton13; 
    private javax.swing.JButton jButton14; 
    private javax.swing.JButton jButton15; 
    private javax.swing.JButton jButton16; 
    private javax.swing.JButton jButton17; 
    private javax.swing.JButton jButton18; 
    private javax.swing.JButton jButton19; 
    private javax.swing.JButton jButton2; 
    private javax.swing.JButton jButton20; 
    private javax.swing.JButton jButton21; 
    private javax.swing.JButton jButton22; 
    private javax.swing.JButton jButton23; 
    private javax.swing.JButton jButton24; 
    private javax.swing.JButton jButton3; 
    private javax.swing.JButton jButton4; 
    private javax.swing.JButton jButton5; 
    private javax.swing.JButton jButton6; 
    private javax.swing.JButton jButton7; 
    private javax.swing.JButton jButton8; 
    private javax.swing.JButton jButton9; 
    private javax.swing.JLabel jLabel1; 
    // End of variables declaration     
} 

Это ошибка, я получаю:

Exception in thread "AWT-EventQueue-0" java.lang.ArithmeticException:/by zero 
at rechnerfinal.RechnerJFrame.jButton24ActionPerformed(RechnerJFrame.java:451) 
at rechnerfinal.RechnerJFrame.access$1700(RechnerJFrame.java:8) 
at rechnerfinal.RechnerJFrame$18.actionPerformed(RechnerJFrame.java:212) 
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) 
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) 
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) 
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) 
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) 
at java.awt.Component.processMouseEvent(Component.java:6533) 
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324) 
at java.awt.Component.processEvent(Component.java:6298) 
at java.awt.Container.processEvent(Container.java:2236) 
at java.awt.Component.dispatchEventImpl(Component.java:4889) 
at java.awt.Container.dispatchEventImpl(Container.java:2294) 
at java.awt.Component.dispatchEvent(Component.java:4711) 
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888) 
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525) 
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466) 
at java.awt.Container.dispatchEventImpl(Container.java:2280) 
at java.awt.Window.dispatchEventImpl(Window.java:2746) 
at java.awt.Component.dispatchEvent(Component.java:4711) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758) 
at java.awt.EventQueue.access$500(EventQueue.java:97) 
at java.awt.EventQueue$3.run(EventQueue.java:709) 
at java.awt.EventQueue$3.run(EventQueue.java:703) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76) 
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86) 
at java.awt.EventQueue$4.run(EventQueue.java:731) 
at java.awt.EventQueue$4.run(EventQueue.java:729) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) 

Также jLabel не отображает результат расчета хотя, когда тестирование с System.out.println, он дал мне правильное решение. Я полностью из идей о том, что может это сделать.

Answer 1

У вас есть несколько вопросов в вашем switch заявления:

switch(Rechenoperation) { 
      case 1: //+ 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1 + value2; 
       setlabeltext(Ergebnis); 
       break; 
      case 2: //- 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1 - value2; 
       setlabeltext(Ergebnis); 
       break; 
      case 3: //x 
       value2 = Integer.valueOf(jLabel1.getText()); 
       Ergebnis = value1 * value2; 
       setlabeltext(Ergebnis); 
       break; 
      case 4: //: 
       value2 = Integer.valueOf(jLabel1.getText()); 
       if(value2 != 0){ //Add a safeguard if value2 is '0' 
        Ergebnis = value1/value2; 
        setlabeltext(Ergebnis); 
       } else { 
        setlabeltext("NaN"); 
       } 
       break; 
     } 

Вы должны разорвать после логики в каждом конкретном случае. Это делает вещи более эффективными и является хорошей практикой. Кроме того, убедитесь, что value2 равен нулю перед делением.

Как указано в FredK, вы можете setlabeltext после оператора switch и получить value2 перед оператором switch. Независимо от того, что это будет иметь значение с максимальной эффективностью, они будут выполняться один раз из-за ваших заявлений break, но он по-прежнему лучше структурирован таким образом для обслуживания.