Update value in Java ArrayList -

i wasn't sure title question, apologies in advance. have value of 50 stored in bidderarray. want able increase 50 given number entered text field.

so want add 10 existing 50, return 60. when add 10 50 replaced 10 instead of adding 2 together. understand why code doing haven't been able find tutorials or hints on should doing instead.

here code:

package abc;  import java.awt.*;   public class funds extends javax.swing.jframe {     int = 0;      bidder bidbal = new bidder();     /** creates new form funds */     public funds() {         initcomponents();     }      private void addactionperformed(java.awt.event.actionevent evt) {         // todo add handling code here:         int f = 0;         boolean validentries = true;          try{             f = integer.parseint(amount.gettext());             bidder.bidderarray.get(i).setregfee(f);         } catch (exception error) {             validentries = false;             amount.setbackground(color.red);         }         if (validentries) {             bidder.exportbidder();             home home = new home();             home.setvisible(true);             this.dispose();         }     } } 

you have current fee, add value, , set fee:

f = integer.parseint(amount.gettext()); bidder.bidderarray.get(i).setregfee( f + bidder.bidderarray.get(i).getregfee() ); 

or add new method bidder class adds fee:

class bidder {     //...     public void addtoregfee( int amount )     {         this.regfee += amount;     } }  f = integer.parseint(amount.gettext()); bidder.bidderarray.get(i).addtoregfee( f );