Error while trying to create a JTable

[Krithika Beri]

I am taking elements from a Dom parser and writing its content into a JTable with TreeSelectionListener() of JTree to indicate which node's data is to be displayed.

private TreeSelectionListener createSelectionListener() {
		return new TreeSelectionListener() {
			
		
			public void valueChanged(TreeSelectionEvent e) {
				

				TreePath path = e.getPath();
				
				TreePath selected_path = e.getNewLeadSelectionPath();
				selected_node = selected_path.getLastPathComponent().toString();
				navpoint = xmlTree.name_compare(selected_node);
				content = xmlTree.content_return();
                                tables();
				
			}
		};

	}

	String selected_node() {
		return selected_node;

	}


	
	void tables ()
	{//JTable table_node;
	

		
		
		String columnName[] = { "Name", "Value" };
	
	Object rowData_node[][] = null;
	Object rowData_content[][] = null;
	JTable table_content = new JTable(rowData_content, columnName);

	NamedNodeMap elementAttributes = navpoint.getAttributes();
	int numAttributes = elementAttributes.getLength();

	for (int j = 0; j < numAttributes; j++) {
		Node attribute = elementAttributes.item(j);

		System.out.println("Node name  :" + attribute.getNodeName());
		System.out.println("Node Value  :"
				+ attribute.getNodeValue());
		System.out.println("j  :"+j);
		rowData_node[j][0] = attribute.getNodeName().toString();
		rowData_node[j][1] = attribute.getNodeValue().toString();

	}
	/*table_node = new JTable(rowData_node, columnName);
	right.add(table_node);
	table_node.setBounds(10, 10, 300, 300);*/
	}
	

[Krithika Beri]

I am getting the following error..

HomeWork1 (class=assessment-practice-tests, container_type=homework, displayName=HomeWork1, id=HomeWork1, playOrder=1)
Node name :class
Node Value :assessment-practice-tests
j :0
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Main.tables(Main.java:166)
at Main$2.valueChanged(Main.java:130)
at javax.swing.JTree.fireValueChanged(Unknown Source)
at javax.swing.JTree$TreeSelectionRedirector.valueChanged(Unknown Source)
at javax.swing.tree.DefaultTreeSelectionModel.fireValueChanged(Unknown Source)
at javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(Unknown Source)
at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPaths(Unknown Source)
at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPath(Unknown Source)
at javax.swing.JTree.setSelectionPath(Unknown Source)
at javax.swing.plaf.basic.BasicTreeUI.selectPathForEvent(Unknown Source)
at javax.swing.plaf.basic.BasicTreeUI$Handler.handleSelection(Unknown Source)
at javax.swing.plaf.basic.BasicTreeUI$Handler.mousePressedDND(Unknown Source)
at javax.swing.plaf.basic.BasicTreeUI$Handler.mousePressed(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[Darryl Burke]

Krithika Beri wrote:I am getting the following error..
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Main.tables(Main.java:166

Which is line 166? What variable(s) is (are) dereferenced on that line?

[Krithika Beri]

rowData_node[j][0] = attribute.getNodeName().toString();

is line 166

[Krithika Beri]

Is there a problem with the Object declaration?

[Krithika Beri]

The problem was with object declaration.
I made the following changes for it to work.

void tables ()
	{JTable table_node;
		
		
		String columnName[] = { "Name", "Value" };
	
	

	NamedNodeMap elementAttributes = navpoint.getAttributes();
	int numAttributes = elementAttributes.getLength();
	
	Object rowData_node[][] = new Object [numAttributes][2];
	Object rowData_content[][] = null;
	JTable table_content = new JTable(rowData_content, columnName);

	for (int j = 0; j < numAttributes; j++) {
		Node attribute = elementAttributes.item(j);

		System.out.println("Node name  :" + attribute.getNodeName());
		System.out.println("Node Value  :"+ attribute.getNodeValue());
		System.out.println("j  :"+j);
		rowData_node[j][0] = attribute.getNodeName().toString();
		rowData_node[j][1] = attribute.getNodeValue().toString();

	}
	table_node = new JTable(rowData_node, columnName);
	right.add(table_node);
	table_node.setBounds(50, 50, 500, 500);
	}