error after pressing cancel button 'C' in calculator (Eclipse IDE and swings)

Question

this is my code for cancel button when i am pressing it before pressing '=' button it is working fine but after pressing '=' when final result is displayed and then if 'C' button is pressed then it showing java.lang.NumberFormatException here is piece of code and 'convert'& 's'is a string

    if(e.getSource() == buttonOp){
                convert = Integer.parseInt(txt.getText());
                System.out.println("parsing done!");
                String choice = e.getActionCommand();
                if(choice.equals("x^2")){
                    txt.setText("");
                    total = convert * convert;
                    System.out.println("total is"+total);
                    s += txt.getText();
                }
                else if(choice.equals("x^3")){
                    txt.setText("");
                    total = convert * convert * convert;
                    s += txt.getText();
                }
                else if (choice.equals("=")){   
                //txt.setText(choice);
                //  number = true;
                    number = false;
                    txt.setText("");
                    System.out.println("pressed '='");
                    if(txt.getText().length() > 0){
                        StringBuilder sb = new StringBuilder(txt.getText());
                        sb.delete(0, txt.getText().length());
                        s = sb.toString();
                    }
                s = Double.toString(total);
                s += txt.getText();
            }
                /*else if (choice.equals("+")){
                    total = convert;

                }*/
                else if(choice.equals("C")){
                    System.out.println("pressing C");
                    if(txt.getText().length()>0){
                        StringBuilder str = new StringBuilder(txt.getText());
                        str.deleteCharAt(txt.getText().length()-1);
                        s = str.toString();
                    }
                    txt.setText(s);
                    }
                }
            else{
                txt.setText(null);
            }
            txt.setText(s);
            }
        });   

here is the output i get pressing 'Ç' after '='

    parsing done!
    total is2601.0
    parsing done!
    pressed '='
    Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException:     For input string: "2601.0"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at cal.Calculator$2.actionPerformed(Calculator.java:95)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

from the exception

....parseInt(Unknown Source)...

...For input string: "2601.0"...

so you are calling parseInt() for a non-int formatted value ("2601.0").

i think your problem is here

if(e.getSource() == buttonOp){
      convert = Integer.parseInt(txt.getText()); // <<<<

so either place this in more proper place (inside the if-else) or use Dobule.parseDouble() as a non-int values are highly possible for a calculator app.