Index: /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/ErrorTreePanel.java
===================================================================
--- /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/ErrorTreePanel.java	(revision 2793)
+++ /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/ErrorTreePanel.java	(revision 2793)
@@ -0,0 +1,156 @@
+package org.openstreetmap.josm.plugins.validator;
+
+import java.util.*;
+import java.util.Map.Entry;
+
+import javax.swing.JTree;
+import javax.swing.tree.*;
+
+import org.openstreetmap.josm.plugins.validator.util.Bag;
+
+/**
+ * A panel that displays the error tree. The selection manager
+ * respects clicks into the selection list. Ctrl-click will remove entries from
+ * the list while single click will make the clicked entry the only selection.
+ *
+ * @author frsantos
+ */
+public class ErrorTreePanel extends JTree
+{
+    /** Serializable ID */
+    private static final long serialVersionUID = 2952292777351992696L;
+
+    /**
+     * The validation data.
+     */
+	protected DefaultTreeModel treeModel = new DefaultTreeModel(new DefaultMutableTreeNode());
+
+    /** The list of errors shown in the tree */
+    private List<TestError> errors;
+    /**
+     * Constructor
+     * @param errors The list of errors
+     */
+    public ErrorTreePanel(List<TestError> errors) 
+    {
+        this.errors = errors;
+        this.setModel(treeModel);
+		this.setRootVisible(false);
+		this.setShowsRootHandles(true);
+		this.expandRow(0);
+		this.setVisibleRowCount(8);
+		this.setCellRenderer(new ErrorTreeRenderer());
+		this.getSelectionModel().setSelectionMode(TreeSelectionModel.DISCONTIGUOUS_TREE_SELECTION);
+        
+        buildTree();
+    }
+
+    /**
+     * Constructor
+     */
+    public ErrorTreePanel() 
+    {
+        this(null);
+    }
+    
+    @Override 
+    public void setVisible(boolean v) 
+    {
+		if (v)
+			buildTree();
+		else 
+			treeModel.setRoot(new DefaultMutableTreeNode());
+		super.setVisible(v);
+	}
+    
+    
+	/**
+	 * Builds the errors tree
+	 */
+	public void buildTree() 
+	{
+		DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode();
+
+		if( errors == null || errors.isEmpty() )
+		{
+			treeModel.setRoot(rootNode);
+			return;
+		}
+		
+		Map<Severity, Bag<String, TestError>> errorTree = new HashMap<Severity, Bag<String, TestError>>();
+		for(Severity s : Severity.values())
+		{
+			errorTree.put(s, new Bag<String, TestError>(20));
+		}
+		
+		for(TestError e : errors)
+		{
+			errorTree.get(e.getSeverity()).add(e.getMessage(), e);
+		}
+		
+		for(Severity s : Severity.values())
+		{
+			Bag<String,	TestError> severityErrors = errorTree.get(s);
+			if( severityErrors.isEmpty() )
+				continue;
+			
+			// Severity node
+			DefaultMutableTreeNode severityNode = new DefaultMutableTreeNode(s);
+			rootNode.add(severityNode);
+			
+			for(Entry<String, List<TestError>> msgErrors : severityErrors.entrySet()  )
+			{
+				// Message node
+				List<TestError> errors = msgErrors.getValue();
+				String msg = msgErrors.getKey() + " (" + errors.size() + ")";
+				DefaultMutableTreeNode messageNode = new DefaultMutableTreeNode(msg);
+				severityNode.add(messageNode);
+				
+				for (TestError error : errors) 
+				{
+					// Error node
+					DefaultMutableTreeNode errorNode = new DefaultMutableTreeNode(error);
+					messageNode.add(errorNode);
+				}
+			}
+		}
+
+		treeModel.setRoot(rootNode);
+		this.scrollRowToVisible(treeModel.getChildCount(rootNode)-1);
+	}
+
+    /**
+     * Set the errors of the tree
+     * @param errors
+     */
+    public void setErrors(List<TestError> errors)
+    {
+        this.errors = errors;
+    }
+    
+    /**
+     * Expands all tree
+     */
+    @SuppressWarnings("unchecked")
+    public void expandAll()
+    {
+        DefaultMutableTreeNode root = (DefaultMutableTreeNode) treeModel.getRoot();
+        
+        int row = 0;
+        Enumeration<DefaultMutableTreeNode> children = root.breadthFirstEnumeration();
+        while( children.hasMoreElements() )
+        {
+            children.nextElement();
+            expandRow(row++);
+        }
+    }
+    
+    /**
+     * Returns the root node model. 
+     * @return The root node model
+     */
+    public DefaultMutableTreeNode getRoot()
+    {
+        return (DefaultMutableTreeNode) treeModel.getRoot();
+    }
+}