content: /*******************************************************************************
   * Copyright (c) 2000, 2007 IBM Corporation and others.
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *     IBM Corporation - initial API and implementation
   *******************************************************************************/
  
  package org.eclipse.wst.jsdt.internal.ui.viewsupport;
  
  import org.eclipse.jface.viewers.Viewer;
  import org.eclipse.jface.viewers.ViewerFilter;
  
  /**
   * filter with a live cycle
   */
  public abstract class JavaViewerFilter extends ViewerFilter {
  
  	private int fCount= 0;
  	
  	/**
  	 * To be overridden by implement
  	 */
  	protected abstract void initFilter();
  	
  	protected abstract void freeFilter();
  	
  	public final void filteringStart() {
  		if (fCount == 0)
  			initFilter();
  		fCount++;
  	}
  	
  	public final void filteringEnd() {
  		fCount--;
  		if (fCount == 0)
  			freeFilter();
  	}
  	
  	/*
   	 * Overrides method from ViewerFilter
   	 */
  	public Object[] filter(Viewer viewer, Object parent, Object[] elements) {
  		try {
  			filteringStart();
  			return super.filter(viewer, parent, elements);
  		} finally {
  			filteringEnd();
  		}
  	}
  
  
  }
  