java - Validation of text fields and contact no text field -

i have jframe consisting of text fields (10) , textarea. want validate text fields , see if not empty , check if 10 digit contact no entered in 1 of text field. after checking text fields, want enable submit button used submit dat database.

i used following code adding text area condition not working,gives error:- exception in thread "awt-eventqueue-0" java.lang.nullpointerexception

here code used not working:-

public class dataentered1 implements documentlistener {     private jbutton button;     list<jtextfield> txtfields=new arraylist<jtextfield>();     jtextarea ta;     public dataentered1(jbutton dbadd)     {         this.button=dbadd;     }     public void addtextfield(jtextfield txtfield)     {         txtfields.add(txtfield);         txtfield.getdocument().adddocumentlistener(this);     }     public void addtextarea(jtextarea ta)     {         this.ta=ta;         ta.getdocument().adddocumentlistener(this);     }     public boolean isdataentered()     {         for(jtextfield txtfield:txtfields)         {             if(txtfield.gettext().length()==0)             return false;         }         return true;     }     public boolean isdata()     {         if(ta.gettext().trim().length()==0)         {              return false;         }         return true;     }     public void insertupdate(documentevent e) {     checkdata();     }     public void removeupdate(documentevent e) {     checkdata();     }     public void changedupdate(documentevent e) {     checkdata();     }     public void checkdata(){     boolean d1=isdataentered();     boolean d2=isdata();     if(d1&&d2)     button.setenabled(true);     } 

}

can me enabling button after validating text fields?

here general purpose class enable/disable button text added/removed group of text fields.

it adds documentlistener documenent of each text field. button ben enable when text has been entered each document:

import java.awt.*; import java.awt.event.*; import java.util.list; import java.util.arraylist; import javax.swing.*; import javax.swing.event.*;  public class dataentered implements documentlistener {     private jbutton button;     private list<jtextfield> textfields = new arraylist<jtextfield>();      public dataentered(jbutton button)     {         this.button = button;     }      public void addtextfield(jtextfield textfield)     {         textfields.add( textfield );         textfield.getdocument().adddocumentlistener( );     }      public boolean isdataentered()     {         (jtextfield textfield : textfields)         {             if (textfield.gettext().trim().length() == 0)                 return false;         }          return true;     }      @override     public void insertupdate(documentevent e)     {         checkdata();     }      @override     public void removeupdate(documentevent e)     {         checkdata();     }      @override     public void changedupdate(documentevent e) {}      private void checkdata()     {         button.setenabled( isdataentered() );     }      private static void createandshowui()     {         jbutton submit = new jbutton( "submit" );         submit.setenabled( false );          jtextfield textfield1 = new jtextfield(10);         jtextfield textfield2 = new jtextfield(10);          dataentered de = new dataentered( submit );         de.addtextfield( textfield1 );         de.addtextfield( textfield2 );          jframe frame = new jframe("sscce");         frame.setdefaultcloseoperation(jframe.exit_on_close);         frame.add(textfield1, borderlayout.west);         frame.add(textfield2, borderlayout.east);         frame.add(submit, borderlayout.south);         frame.pack();         frame.setlocationbyplatform( true );         frame.setvisible( true );     }      public static void main(string[] args)     {         eventqueue.invokelater(new runnable()         {             public void run()             {                 createandshowui();             }         });     } } 

also check if 10 digit contact no entered in 1 of text field.

you need customize isdataentered() method add check additional requirement.