java - JTextField set input limit -


hi trying use setdocument method limit number of characters user can input in text field. somehow not limit no of input characters. here's code

import javax.swing.text.attributeset; import javax.swing.text.badlocationexception; import javax.swing.text.plaindocument;   public class jtextfieldcharlimit extends plaindocument {       private int limit;      public jtextfieldcharlimit(int limit)     {         super();         this.limit = limit;     }     public void inserstring(int offset, string str, attributeset set) throws badlocationexception     {         if(str == null)         {             return;         } else if((getlength() + str.length()) <= limit)         {             str = str.touppercase();             super.insertstring(offset, str, set);         }     }     }

i using class in class have declared text field follows:

void playerinfoscreen(jframe mainframe, jpanel menupanel)     {         final screenconstructor playername = new screenconstructor();         final jframe frame = mainframe;         final jpanel returnpanel = menupanel;          final jpanel panel = playername.createpanel("menu panel");          final jbutton returnbutton = playername.createbutton("main menu");         final jtextfield textentry = playername.createtextfield(10);                 // text field length needs set prevent long texts         final jlabel label = playername.createlabel("enter player name:");          playername.addbuttontopanel(panel, returnbutton);         playername.addlabeltopanel(panel, label);         playername.addjtextfieldtopanel(panel, textentry);          textentry.setdocument(new jtextfieldcharlimit(5));         playername.displayscreen(frame, panel);             // check esc button let user return main menu             textentry.addactionlistener(new actionlistener()         {             public void actionperformed(actionevent e)             {                 string player = textentry.gettext(); // save entered player name                 storedplayername = player; // store player in order use in highscores , display on game screen                 gamescreen game = new gamescreen(frame, panel); // go game screen              }         });           returnbutton.addactionlistener(new actionlistener()         {             public void actionperformed(actionevent e)             {                 frame.setcontentpane(returnpanel); // go previous panel             }         });         }

use documentfilter. see implementing document filter , documentfilter examples more details.

public class sizefilter extends documentfilter {      private int maxcharacters;          public sizefilter(int maxchars) {         maxcharacters = maxchars;     }      public void insertstring(filterbypass fb, int offs, string str, attributeset a)             throws badlocationexception {          if ((fb.getdocument().getlength() + str.length()) <= maxcharacters)             super.insertstring(fb, offs, str, a);         else             toolkit.getdefaulttoolkit().beep();     }      public void replace(filterbypass fb, int offs, int length, string str, attributeset a)             throws badlocationexception {          if ((fb.getdocument().getlength() + str.length()                 - length) <= maxcharacters)             super.replace(fb, offs, length, str, a);         else             toolkit.getdefaulttoolkit().beep();     } }

credit mdp

((abstractdocument)textentry.getdocument()).setdocumentfilter(new sizefilter(5));

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