How To limit the number of characters in JTextField

Question

How to limit the number of characters entered in a JTextField   Suppose I want to enter say 5 characters max  After that no characters can be entered into it

User · Answer

Just Try This    textfield addKeyListener new java awt event KeyAdapter         public void keyTyped java awt event KeyEvent evt            if textfield getText   length   gt  5 amp  amp   evt getKeyChar    KeyEvent VK DELETE  evt getKeyChar    KeyEvent VK BACK SPACE                 getToolkit   beep                evt consume

User · Answer

Just put this code in KeyTyped event       if   jtextField getText     evt getKeyChar    length    gt  20            evt consume            Where  20  is the maximum number of characters that you want

User · Answer

Read the section from the Swing tutorial on Implementing a DocumentFilter for a more current solution   This solution will work an any Document  not just a PlainDocument   This is a more current solution than the one accepted

User · Answer

import java awt KeyboardFocusManager  import javax swing InputVerifier  import javax swing JTextField  import javax swing text AbstractDocument  import javax swing text AttributeSet  import javax swing text BadLocationException  import javax swing text DocumentFilter  import javax swing text DocumentFilter FilterBypass              author Igor     public class CustomLengthTextField extends JTextField        protected boolean upper   false      protected int maxlength   0       public CustomLengthTextField             this -1              public CustomLengthTextField int length  boolean upper            this length  upper  null              public CustomLengthTextField int length  InputVerifier inpVer            this length  false  inpVer                                 param length - maksimalan length         param upper - turn it to upercase         param inpVer - InputVerifier             public CustomLengthTextField int length  boolean upper  InputVerifier inpVer            super            this maxlength   length          this upper   upper          if  length  gt  0                AbstractDocument doc    AbstractDocument  getDocument                doc setDocumentFilter new DocumentSizeFilter                       setInputVerifier inpVer              public CustomLengthTextField int length            this length  false              public void setMaxLength int length            this maxlength   length             class DocumentSizeFilter extends DocumentFilter            public void insertString FilterBypass fb  int offs  String str  AttributeSet a                  throws BadLocationException                  This rejects the entire insertion if it would make               the contents too long  Another option would be               to truncate the inserted string so the contents               would be exactly maxCharacters in length              if   fb getDocument   getLength     str length     lt   maxlength                    super insertString fb  offs  str  a                                    public void replace FilterBypass fb  int offs                  int length                  String str  AttributeSet a                  throws BadLocationException                if  upper                    str   str toUpperCase                                 This rejects the entire replacement if it would make               the contents too long  Another option would be               to truncate the replacement string so the contents               would be exactly maxCharacters in length              int charLength   fb getDocument   getLength     str length   - length               if  charLength  lt   maxlength                    super replace fb  offs  length  str  a                   if  charLength    maxlength                        focusNextComponent                                    else                   focusNextComponent                                     private void focusNextComponent                 if  CustomLengthTextField this    KeyboardFocusManager getCurrentKeyboardFocusManager   getFocusOwner                      KeyboardFocusManager getCurrentKeyboardFocusManager   focusNextComponent

User · Answer

Great question  and it s odd that the Swing toolkit doesn t include this functionality natively for JTextFields  But  here s a great answer from my Udemy com course  Learn Java Like a Kid    txtGuess   new JTextField    txtGuess addKeyListener new KeyAdapter         public void keyTyped KeyEvent e             if  txtGuess getText   length    gt   3      limit textfield to 3 characters             e consume                   This limits the number of characters in a guessing game text field to 3 characters  by overriding the keyTyped event and checking to see if the textfield already has 3 characters - if so  you re  consuming  the key event  e  so that it doesn t get processed like normal

User · Answer

I have solved this problem by using the following code segment   private void jTextField1KeyTyped java awt event KeyEvent evt        boolean max   jTextField1 getText   length    gt  4      if   max            evt consume

User · Answer

http   www rgagnon com javadetails java-0198 html  import javax swing text PlainDocument  import javax swing text AttributeSet  import javax swing text BadLocationException   public class JTextFieldLimit extends PlainDocument     private int limit     JTextFieldLimit int limit       super       this limit   limit          public void insertString  int offset  String  str  AttributeSet attr   throws BadLocationException       if  str    null  return       if   getLength     str length     lt   limit          super insertString offset  str  attr                 Then  import java awt    import javax swing      public class DemoJTextFieldWithLimit extends JApplet     JTextField textfield1     JLabel label1      public void init          getContentPane   setLayout new FlowLayout                  label1   new JLabel  max 10 chars         textfield1   new JTextField 15        getContentPane   add label1        getContentPane   add textfield1        textfield1 setDocument          new JTextFieldLimit 10                first result from google

User · Answer

If you wanna have everything into one only piece of code  then you can mix tim s answer with the example s approach found on the API for JTextField  and you ll get something like this   public class JTextFieldLimit extends JTextField       private int limit       public JTextFieldLimit int limit            super            this limit   limit              Override     protected Document createDefaultModel             return new LimitDocument               private class LimitDocument extends PlainDocument             Override         public void insertString  int offset  String  str  AttributeSet attr   throws BadLocationException               if  str    null  return               if   getLength     str length     lt   limit                    super insertString offset  str  attr                                              Then there is no need to add a Document to the JTextFieldLimit due to JTextFieldLimit already have the functionality inside

[java] How To limit the number of characters in JTextField?

Examples related to java

Examples related to swing