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  package org.apache.cayenne.exp;
  
  import static org.junit.Assert.assertEquals;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import org.junit.Assert;
  
  /**
   * Class that collects statistics of expression traversal.
   */
  public class TstTraversalHandler implements TraversalHandler {
  	protected List<Object> treeFlatView = new ArrayList<>();
  	protected int children;
  	protected int nodes;
  	protected int nodesStarted;
  	protected int leafs;
  
  	/**
  	 * Performs independent traversal of two expressions, comparing the results.
  	 * If expressions structure is different, throws an exception.
  	 */
  	public static void compareExps(Expression exp1, Expression exp2) {
  		TstTraversalHandler handler1 = new TstTraversalHandler();
  		handler1.traverseExpression(exp1);
  
  		TstTraversalHandler handler2 = new TstTraversalHandler();
  		handler2.traverseExpression(exp2);
  
  		assertEquals(handler1.nodes, handler2.nodes);
  	}
  
  	public TstTraversalHandler() {
  
  	}
  
  	public void assertConsistency() {
  		Assert.assertEquals(nodesStarted, nodes);
  	}
  
  	public void traverseExpression(Expression exp) {
  		reset();
  		exp.traverse(this);
  	}
  
  	public void reset() {
  		children = 0;
  		nodes = 0;
  		nodesStarted = 0;
  		leafs = 0;
  	}
  
  	public int getNodeCount() {
  		return nodes;
  	}
  
  	public int getChildren() {
  		return children;
  	}
  
  	public int getNodes() {
  		return nodes;
  	}
  
  	public int getLeafs() {
  		return leafs;
  	}
  
  	public void finishedChild(Expression node, int childIndex,
  			boolean hasMoreChildren) {
  		children++;
  	}
  
  	public void startNode(Expression node, Expression parentNode) {
  		treeFlatView.add(node);
  		nodesStarted++;
  	}
  
  	public void endNode(Expression node, Expression parentNode) {
  		nodes++;
  	}
  
  	public void objectNode(Object leaf, Expression parentNode) {
  		treeFlatView.add(leaf);
  		leafs++;
  	}
  }
  