NetBeans Java Calculator - Need help with assignment - Got TeamViewer

[Zertacus]

Hello!

I am using NetBeans 7.2.1 to make a Java Calculator, but I have a problem with using diffrent "operations" in the same calculation.

Example,
5+5+5+5=20, it works
but
5+5+5-5=0, this is where it fails...

(((( MY CODE FOR "+" ))))))))))

MetodCheck=1;  
if(MetodCheck==2){
            Tal2=(Double.parseDouble(String.valueOf(display.getText())));
        Tal1=Tal1+Tal2;
        display.setText(String.valueOf(Tal1));
        Tal2=0;
        Clearat=1;
    
}
if(MetodCheck==3){
            Tal2=(Double.parseDouble(String.valueOf(display.getText())));
        Tal1=Tal1+Tal2;
        display.setText(String.valueOf(Tal1));
        Tal2=0;
        Clearat=1;
}
if(MetodCheck==4){
            Tal2=(Double.parseDouble(String.valueOf(display.getText())));
        Tal1=Tal1+Tal2;
        display.setText(String.valueOf(Tal1));
        Tal2=0;
        Clearat=1;
}
      if(PlusCheck==0){
            Tal1=(Double.parseDouble(String.valueOf(display.getText())));
            // §§Tal1=Tal1+Tal2;
            display.setText("");
            MetodCheck=1;
        
       
        }
        
      else if(PlusCheck>=0){
            
        Tal2=(Double.parseDouble(String.valueOf(display.getText())));
        Tal1=Tal1+Tal2;
        display.setText(String.valueOf(Tal1));
        Tal2=0;
        Clearat=1;
         }
        
        PlusCheck++;
        decimalKlickat=0;

I could really use some help, if someone wants to connect to TeamViewer, just PM me :)