java - Using Document FIlter to filter multiple periods(.) -

lets user has input double value jtextfield gets calculated.
if user used more 1 period trigger numberformatexception, assume solution using document filter filter out periods or catching exception , notifying user of invalid input

currenty using documentfilter allow digits , periods, problem how filter out second period

plaindocument filter = new plaindocument();             filter.setdocumentfilter(new documentfilter() {                     @override                     public void insertstring(filterbypass fb, int off, string str, attributeset attr)                      throws badlocationexception                      {                     fb.insertstring(off, str.replaceall("[^0-9.]", ""), attr);                     }                      @override                     public void replace(filterbypass fb, int off, int len, string str, attributeset attr)                      throws badlocationexception                      {                     fb.replace(off, len, str.replaceall("[^0-9.]", ""), attr);                     }             });              apm.setdocument(filter); 

example

invalid input: 1.2.2

valid input: 1.22

my suggestion change overridden insertstring , replace methods checks whether "." has been inserted earlier before insert or replace , change filter in way 'period' replaced blank string if subsequent time period character inserted user. have illustrated below:

@override public void insertstring(filterbypass fb, int off, string str, attributeset attr)                  throws badlocationexception {     string regexp;     document doc = fb.getdocument();     if(doc.gettext(0, doc.getlength()).indexof(".") == -1){         regexp = "[^0-9.]";     } else {         regexp = "[^0-9]";     }     fb.insertstring(off, str.replaceall(regexp, ""), attr); }  @override public void replace(filterbypass fb, int off, int len, string str, attributeset attr)                  throws badlocationexception {     string regexp;     document doc = fb.getdocument();     if(doc.gettext(0, doc.getlength()).indexof(".") == -1){         regexp = "[^0-9.]";     } else {         regexp = "[^0-9]";     }     fb.replace(off, len, str.replaceall(regexp, ""), attr); } 

the above code allow 'period' inserted once in document documentfilter set.