Help with DOM.I am trying to access the nodes acc. to their levels in an xml file.reached upto 3-4 levels then getting a nullpointer exception.Please help...wat datastructure would better suit this.i need to index all the nodes.the xml file is cs.xml given under and the java code below tht.
<department>
<deptname>Computer Sciences</deptname>
<gradstudent>
<name>
<lastname>Aboulnaga</lastname>
<firstname>Ashraf</firstname>
</name>
<phone>2626623</phone>
<email>ashraf@cs.wisc.edu</email>
<address>
<city>Madison</city>
<state>WI</state>
<zip>53705</zip>
</address>
<office>7360</office>
<url>www.cs.wisc.edu/~ashraf</url>
<gpa>4.0</gpa>
</gradstudent>
<gradstudent>
<name>
<lastname>Ailamaki</lastname>
<firstname>Anastasia</firstname>
</name>
<phone>2652311</phone>
<email>natassa@cs.wisc.edu</email>
<address>
<city>Madison</city>
<state>WI</state>
<zip>53706</zip>
</address>
<address>
<city>Madison</city>
<state>WI</state>
<zip>53706</zip>
</address>
<office>7351</office>
<url>www.cs.wisc.edu/~natassa</url>
<gpa>4.0</gpa>
</gradstudent>
</department>
import org.w3c.dom.*;
import org.w3c.dom.Element.*;
import javax.xml.parsers.*;
import java.io.*;
import org.xml.sax.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
public class project1{
public static void main(String[] args) {
try{
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter xml file name: ");
String str = bf.readLine();
String child[][]=new String[100][100];
String parent[]=new String[100];
String node[]=new String[100];
String arr[][]=new String[100][100];
NodeList fstNm1[][]=new NodeList[100][100];
File file = new File(str);
if (file.exists()){
DocumentBuilderFactory fact = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = fact.newDocumentBuilder();
Document doc = builder.parse(str);
NodeList list = doc.getElementsByTagName("*");
int num=0,p1=num,p2=num;
//L-0
Element element = (Element)list.item(0);//root node
node[num]=element.getNodeName();
Node n=element.getParentNode();//root's parent node #doc
parent[num]=n.getNodeName();
NodeList fstNm = element.getChildNodes();//childs of root
System.out.println("Node no: "+(num)+ " has name " +element.getNodeName()+" parent name "+n.getNodeName()+" and no.of childs is "+(fstNm.getLength()-1)/2);
for(int j=1,k=0;j<fstNm.getLength();j+=2,k++)
{
System.out.println("Child: " + j/2 + " is " + fstNm.item(j).getNodeName()+" Parent: "+fstNm.item(j).getParentNode().getNodeName() );
child[num][k]=fstNm.item(j).getNodeName();
}
num++;
p1=num;
System.out.println((fstNm.getLength()-1)/2);
//L-1
for(int i=1,y=0;i<fstNm.getLength();i+=2,y++)
{
Element element1 = (Element)fstNm.item(i);
node[num]=element1.getNodeName();
Node n1=element1.getParentNode();
parent[num]=n1.getNodeName();
fstNm1[1][y] = element1.getChildNodes();
System.out.println("Node no: "+num+ " has name " + element1.getNodeName()+" parent name "+n1.getNodeName()+" and no.of childs is "+(fstNm1[1][y].getLength()-1)/2);
if((fstNm1[1][y].getLength()-1)/2==0)
{
child[num][0]="No Childs";
}
else
{
for(int j=1,k=0;j<fstNm1[1][y].getLength();j+=2,k++)
{
System.out.println("Child: " + j/2 + " is " + fstNm1[1][y].item(j).getNodeName()+" Parent: "+fstNm1[1][y].item(j).getParentNode().getNodeName() );
child[num][k]=fstNm1[1][y].item(j).getNodeName();
}
}
num++;
}
p2=num;
//L-2
for(int y=0;p1<p2;p1++,y++)
{
for(int i=1;i<fstNm1[1][y].getLength();i+=2)
{
Element element2 = (Element)fstNm1[1][y].item(i);
node[num]=element2.getNodeName();
Node n2=element2.getParentNode();
parent[num]=n2.getNodeName();
fstNm1[2][y] = element2.getChildNodes();
System.out.println("Node no:"+num+ " has name " + element2.getNodeName()+" parent name: "+n2.getNodeName()+" and no.of childs is "+(fstNm1[2][y].getLength()-1)/2);
if((fstNm1[2][y].getLength()-1)/2==0)
{
child[num][0]="No Childs";
}
else
{
for(int j=1,k=0;j<fstNm1[2][y].getLength();j+=2,k++)
{
System.out.println("Child: " + j/2 + " is " + fstNm1[2][y].item(j).getNodeName()+" Parent: "+fstNm1[2][y].item(j).getParentNode().getNodeName() );
child[num][k]=fstNm1[2][y].item(j).getNodeName();
}
}
num++;
}
}
p2=num;
//L-3
for(int y=0;p1<p2;p1++,y++)
{
for(int i=1;i<fstNm1[2][y].getLength();i+=2)
{
Element element2 = (Element)fstNm1[2][y].item(i);
node[num]=element2.getNodeName();
Node n2=element2.getParentNode();
parent[num]=n2.getNodeName();
fstNm1[3][y] = element2.getChildNodes();
System.out.println("Node no: "+num+ " has name: " + element2.getNodeName()+" parent name: "+n2.getNodeName()+" and no.of childs is "+(fstNm1[3][y].getLength()-1)/2);
if((fstNm1[3][y].getLength()-1)/2==0)
{
child[num][0]="No Childs";
}
else
{
for(int j=1,k=0;j<fstNm1[3][y].getLength();j+=2,k++)
{
System.out.println("Child: " + j/2 + " is " + fstNm1[3][y].item(j).getNodeName()+" Parent: "+fstNm1[3][y].item(j).getParentNode().getNodeName() );
child[num][k]=fstNm1[3][y].item(j).getNodeName();
}
}
num++;
}
}
for(int i=0;i<num;i++)
{
System.out.println("Node name is "+node[i]+" Parent Name is "+parent[i]+" Child names are ");
for(int j=0;j<100;j++)
{
if((child[i][j]!=null))
System.out.println(child[i][j]+(i)+" "+j);
}
}
}
else{
System.out.println("File not found!");
}
}
catch(Exception e){
System.out.println("Exception "+e);}
}
}
