content: package com.japisoft.framework.ui.text;
  
  import java.awt.Color;
  
  import javax.swing.JTextField;
  import javax.swing.UIManager;
  import javax.swing.text.AttributeSet;
  import javax.swing.text.BadLocationException;
  import javax.swing.text.PlainDocument;
  
  /**
  This program is available under two licenses : 
  
  1. For non commercial usage : 
  
  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
  
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  
  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
  2. For commercial usage :
  
  You need to get a commercial license for source usage at : 
  
  http://www.editix.com/buy.html
  
  Copyright (c) 2018 Alexandre Brillant - JAPISOFT SARL - http://www.japisoft.com
  
  @author Alexandre Brillant - abrillant@japisoft.com
  @author JAPISOFT SARL - http://www.japisoft.com
  
  */
  public class EmptyColoredTextField extends JTextField {
  	
  	private Color emptyColor = null;
  	private Color okColor = null;
  	
  	public EmptyColoredTextField(
  			Color emptyColor,
  			Color okColor ) {
  		this.emptyColor = emptyColor;
  		this.okColor = okColor;
  		updateColor();
  		setDocument( new CustomPlainDocument() );
  	}
  
  	/** It will used the color from the keys of the UIManager : 
  	 * - EmptyColoredTextField.emptyColor
  	 * - EmptyColoredTextField.okColor
  	 */
  	public EmptyColoredTextField() {
  		emptyColor = UIManager.getColor( "EmptyColoredTextField.emptyColor" );
  		okColor = UIManager.getColor( "EmptyColoredTextField.okColor" );
  		updateColor();
  		setDocument( new CustomPlainDocument() );
  	}
  
  	private void updateColor() {
  		if ( emptyColor == null || okColor == null )
  			return;
  		if ( getDocument().getLength() == 0 ) {
  			if ( getBackground() != emptyColor )
  				setBackground( emptyColor );
  		}
  		else {
  			if ( getBackground() != okColor )
  				setBackground( okColor );
  		}
  	}
  	
  	class CustomPlainDocument extends PlainDocument {
  		public void insertString(int offs, String str, AttributeSet a)
  				throws BadLocationException {
  			super.insertString(offs, str, a);
  			updateColor();
  		}
  		public void remove(int offs, int len) throws BadLocationException {
  			super.remove(offs, len);
  			updateColor();
  		}
  	}
  }
  