java - trouble passing input from one JTextArea into another JTextArea -

my issue lies in documentlister arealistener. can't seem figure out how pass in text user enters 1 of jtextareas conversions , return other jtextarea.

the goal of program take in user entered roman or arabic number in 1 of fields, convert , return value of conversion other field in real time.

my gui , conversion methods work, can't seem wrap head around obtaining string user , printing in real time.

public class arabictoromangui_hard extends jframe { private static final long serialversionuid = 1l;  jpanel panel = new jpanel();   //constructor add text fields frame public arabictoromangui_hard() {        jtextarea left = new jtextarea(10, 20);     jtextarea right = new jtextarea(10, 20);     setlayout(new gridlayout(1, 2));      add(new jscrollpane(left));     add(new jscrollpane(right));      mirrordocument leftdoc = new mirrordocument();     mirrordocument rightdoc = new mirrordocument();      left.setdocument(leftdoc);     right.setdocument(rightdoc);      leftdoc.adddocumentlistener(new documenthandler(rightdoc));     rightdoc.adddocumentlistener(new documenthandler(leftdoc));      leftdoc.getdocument().adddocumentlistener(arealistener);     rightdoc.getdocument().adddocumentlistener(arealistener);    }    documentlistener listener = new documentlistener()  public class arealistener implements documentlistener {     //documentlistener listener = new documentlistener()          @override         public void changedupdate(documentevent e)          {             convertinput();         }          @override         public void insertupdate(documentevent e)          {             convertinput();          }          @override         public void removeupdate(documentevent e)          {             convertinput();          }         private void convertinput(documentevent e)         {             boolean arabicentered = false;             boolean romanentered = false;              (char ch : userinputtedtext.tochararray())             {                 if(character.isletter(ch))                 {                     romanentered = true;                 }                 if(character.isdigit(ch))                 {                     arabicentered = true;                 }                        }              if(romanentered = true)             {                 if(conversionlogic_hard.getcheckfail() == false)                 {                 conversionlogic_hard.convertfromromantoarabic(userinputtedtext); //converts string of romannumerals arabic int                 string arabicnumberasstring = conversionlogic_hard.getconvertedromannumeral(); //converts number int string                 }             }             if(arabicentered == true)             {                 if(conversionlogic_hard.getcheckfail() == false)                 {                 conversionlogic_hard.convertfromarabictoroman(userinputtedtext); //converts string arabicnumberal string roman numberal                 string romannumberalasstring = conversionlogic_hard.getconvertedromannumeral(); //gets romannumberal string                 }             }            }//end convertinput   }//end arealistener  //creates flag test state of textarea     public class mirrordocument extends plaindocument     {         private boolean ignoreupdatedtext;         public void setignoreupdates(boolean ignoreupdatestext)         {             this.ignoreupdatedtext = ignoreupdatestext;         }         public boolean isignoreupdates()         {             return ignoreupdatedtext;         }     }  //when event occurs checks ignoreupdatedtext flag of document check if false. //then sets flag in checkdocument true prevent document listener processing new events. //then updates checkdocument. public static class documenthandler implements documentlistener {     private mirrordocument checkdocument;     private boolean ignoreupdatedtext = false;     private jtextarea leftdoc, rightdoc;     boolean arabicentered = false;     boolean romanentered = false;       public documenthandler(mirrordocument checkdocument)     {         this.checkdocument = checkdocument;     }      @override     public void removeupdate(documentevent e)      {         document doc = e.getdocument();         if (doc instanceof mirrordocument)         {             mirrordocument mirrordoc = (mirrordocument) doc;             if (!mirrordoc.isignoreupdates())              {                 try                  {                     checkdocument.setignoreupdates(true);                     checkdocument.remove(e.getoffset(), e.getlength());                 }                  catch (badlocationexception exc)                  {                     exc.printstacktrace();                 }                                   {                     checkdocument.setignoreupdates(false);                 }             }         }        }//end removeupdate      @override     public void changedupdate(documentevent e)      {         //not used       }      @override     public void insertupdate(documentevent e)      {         document doc = e.getdocument();         if (doc instanceof mirrordocument)         {             mirrordocument mirrordoc = (mirrordocument) doc;             if( !mirrordoc.isignoreupdates())             {                 try                 {                     string textinput = e.getdocument().gettext(e.getoffset(), e.getlength());                     checkdocument.setignoreupdates(true);                     checkdocument.insertstring(e.getoffset(), textinput, null);                 }                 catch(badlocationexception exc)                 {                     exc.printstacktrace();                 }                                 {                     checkdocument.setignoreupdates(false);                 }             }         }     }//end insertupdate      } }//class 

you can use documentfilter listen changes.

when create documentfilter can specify text field updated converted text.

using approach can remove documentfilter text field before set text avoid recursion of 2 text fields trying update 1 another.

the filter might like:

import javax.swing.*; import javax.swing.text.*; import java.awt.toolkit;  public class conversionfilter extends documentfilter {     private boolean arabic;     private jtextfield converted;      public conversionfilter(boolean arabic, jtextfield converted)     {         this.arabic = arabic;         this.converted = converted;     }      @override     public void insertstring(filterbypass fb, int offs, string str, attributeset a)         throws badlocationexception     {         super.insertstring(fb, offs, str, a);          convertinput(fb);     }      @override     public void replace(final filterbypass fb, final int offs, final int length, final string str, final attributeset a)         throws badlocationexception     {         super.replace(fb, offs, length, str, a);         convertinput(fb);     }      @override     public void remove(documentfilter.filterbypass fb, int offset, int length)         throws badlocationexception     {         super.remove(fb, offset, length);         convertinput(fb);     }      private void convertinput(documentfilter.filterbypass fb)     {         //  remove documentfilter text field converted          abstractdocument document = (abstractdocument)converted.getdocument();         documentfilter df = document.getdocumentfilter();         document.setdocumentfilter( null );          //  conversion , update text field          string text = fb.getdocument().gettext();         string convertedtext = arabic ? converttoroman(text) : converttoarabic(text);         converted.settext( convertedtext );          //  restore documentfilter on converted text field          document.setdocumentfilter( df );     } } 

then use filter code might like:

jtextfield arabictextfield = new jtextfield(...); jtextfield romantextfield = new jtextfield(...);  abstractdocument arabicdocument = (abstractdocument)arabictextfield.getdocument(); arabicdocument.setdocumentfilter( new conversonfilter(true, romantextfield) );  abstractdocument romandocument = (abstractdocument)romantextfield.getdocument(); romandocument.setdocumentfilter( new conversonfilter(false, arabictextfield) ); 

i used documentfilter instead of documentlistener notified of changes document because of getter/setter method documentfilter make easy remove , restore filter.