JTextField is a lightweight component that allows the editing of a single line of text. For information on and examples of using text fields, see How to Use Text Fields in The Java Tutorial.

JTextField is intended to be source-compatible with java.awt.TextField where it is reasonable to do so. This component has capabilities not found in the java.awt.TextField class. The superclass should be consulted for additional capabilities.

JTextField has a method to establish the string used as the command string for the action event that gets fired. The java.awt.TextField used the text of the field as the command string for the ActionEvent. JTextField will use the command string set with the setActionCommand method if not null, otherwise it will use the text of the field as a compatibility with java.awt.TextField.

The method setEchoChar and getEchoChar are not provided directly to avoid a new implementation of a pluggable look-and-feel inadvertently exposing password characters. To provide password-like services a separate class JPasswordField extends JTextField to provide this service with an independently pluggable look-and-feel.

The java.awt.TextField could be monitored for changes by adding a TextListener for TextEvent's. In the JTextComponent based components, changes are broadcasted from the model via a DocumentEvent to DocumentListeners. The DocumentEvent gives the location of the change and the kind of change if desired. The code fragment might look something like:

     DocumentListener myListener = ??;
     JTextField myArea = ??;
     myArea.getDocument().addDocumentListener(myListener);
 

The horizontal alignment of JTextField can be set to be left justified, leading justified, centered, right justified or trailing justified. Right/trailing justification is useful if the required size of the field text is smaller than the size allocated to it. This is determined by the setHorizontalAlignment and getHorizontalAlignment methods. The default is to be leading justified.

For the keyboard keys used by this component in the standard Look and Feel (L&F) renditions, see the JTextField key assignments.

How the text field consumes VK_ENTER events depends on whether the text field has any action listeners. If so, then VK_ENTER results in the listeners getting an ActionEvent, and the VK_ENTER event is consumed. This is compatible with how AWT text fields handle VK_ENTER events. If the text field has no action listeners, then as of v 1.3 the VK_ENTER event is not consumed. Instead, the bindings of ancestor components are processed, which enables the default button feature of JFC/Swing to work.

Customized fields can easily be created by extending the model and changing the default model provided. For example, the following piece of code will create a field that holds only upper case characters. It will work even if text is pasted into from the clipboard or it is altered via programmatic changes.

 public class UpperCaseField extends JTextField {
 
     public UpperCaseField(int cols) {
         super(cols);
     }
 
     protected Document createDefaultModel() {
 	      return new UpperCaseDocument();
     }
 
     static class UpperCaseDocument extends PlainDocument {
 
         public void insertString(int offs, String str, AttributeSet a) 
 	          throws BadLocationException {
 
 	          if (str == null) {
 		      return;
 	          }
 	          char[] upper = str.toCharArray();
 	          for (int i = 0; i < upper.length; i++) {
 		      upper[i] = Character.toUpperCase(upper[i]);
 	          }
 	          super.insertString(offs, new String(upper), a);
 	      }
     }
 }

 

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see {@link java.beans.XMLEncoder}.