java - JOptionPane.showMessageDialog keeps reappearing -

my code supposed ensure users enter binary string. goes right , in order if enter correct binary number (1, 0). when enter wrong number (alphabet or number other 0 , 1) joptionpane.showmessagedialog appears showing error message, , when click "ok" or "cross" button reappears again. close app have use process manager kill "java.exe".

here complete code app:

import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.*;  class bn extends jframe {     private jlabel l1;     private jlabel l2;     private jlabel l3;      private jtextfield tf;      private jbutton oc;     private jbutton hd;     private jbutton dc;  public bn() {     settitle("binary conversion");     setsize(350 , 190);     setresizable(false);     setlocation(720 , 200);     //setdefaultcloseoperation(jframe.exit_on_close);     setlayout(new flowlayout(flowlayout.center, 25, 10));      l1 = new jlabel(">>>>>>>>binary conversion<<<<<<<<");     l2 = new jlabel("enter number:");     l3 = new jlabel("                                    convert to:                                    ");      tf = new jtextfield(25);      oc = new jbutton("octal");     hd = new jbutton("hexa decimal");     dc = new jbutton("decimal");      add(l1); // binary conversion     add(l2); // enter number      add(tf); // text field      add(l3); // conver       add(oc); // octal     add(hd); // hexa decimal     add(dc); // decimal      oc.addactionlistener(new cvr());     hd.addactionlistener(new cvr());     dc.addactionlistener(new cvr());      setvisible(true); }  void res() {     int b = 0;     string num = tf.gettext();     int , l;     l = num.length();     char ch;          {         (i=0 ; i<l ; i++)         {             b = 0;             ch = num.charat(i);             if (character.isdigit(ch) && (ch == 48 || ch == 49))                 b=1;             else             {                 joptionpane.showmessagedialog(null, "please enter binary number (1 , 0)");             }         }     }     while(b != 1); }   void occ() {     res();      string num = tf.gettext();      long dec = long.parselong(num,2);      string oct = long.tooctalstring(dec);      joptionpane.showmessagedialog(null, "octal equivalent is: "+ oct); }  void hdc() {     res();      string num = tf.gettext();      long dec = integer.parseint(num,2);      string hex = long.tohexstring(dec);      joptionpane.showmessagedialog(null, "hexa decimal equivalent is: "+ hex);  }  void dcc() {     res();      string num = tf.gettext();     long decimal = 0, temp, = 0;     temp = long.parselong(num);     while (temp != 0) {         long r = temp % 10;         long value = r * (int)math.pow(2, i);         i++;         decimal = decimal + value;         temp /= 10;     }     joptionpane.showmessagedialog(null, "decimal equivalent is: "+ decimal); }   private class cvr implements actionlistener {     public void actionperformed(actionevent e)     {         if (e.getsource() == oc)         {             occ();         }          if (e.getsource() == hd)         {             hdc();         }          if (e.getsource() == dc)         {             dcc();         }     } }  public static void main(string args[]) {     bn obj = new bn(); } }  

the code joptionpane located in void res() method. how can close dialog pane may reenter value input?

remove { } while loop

do {    (i=0 ; < l ; i++)     {         b = 0;         ch = num.charat(i);         if (character.isdigit(ch) && (ch == 48 || ch == 49))             b=1;         else         {             joptionpane.showmessagedialog(null, "please enter binary number (1 , 0)");         }     } } while(b != 1);