Assignment 1

Frequently Asked Questions

• When running javac I get an error that package org.apache.xerces.parsers does not exist.
  You might need to compile using

  javac -cp /usr/share/java/xerces.jar file.java

  or with

  javac -cp /usr/share/java/xercesImpl.jar file.java

• In the example, you used an XML file with only text, attribute and element nodes.
  Does it mean that we don't need to consider document node, entity node, comment node and so on?
  No. In some cases you have to consider more types of nodes.
  For instance, to count the total number of nodes, in the "-s" option, you should consider 6 different types of nodes:

  "do not count the extra document node provided by DOM (only count element,
  processing instruction, comment, attribute, text, and CDATA nodes)"

  For other things, such as determining the maximal height of the tree, you should only care about element and text nodes.

• In the example:

  <book isbn="1-2345-6789-0" year="1994">
  <title>TCP/IP Illustrated</title>
  <author><last>Stevens</last><first>John</first></author>
  <publisher>Addison-Wesley</publisher>
  <price currency="USD">65.95</price>
  </book>
  

  I only see two nodes that have attributes, the <book> node and the <price> node. But your answer is "Number of attribute nodes: 3". Why?

  In DOM, everything is a node. So, the attribute "isbn" with value "1-2345-6789-0" is one node (of type attribute). Then there is another attribute node for the attribute "year" (with value "1994"), and a third attribute node with name "currency" and value "USD". So, we do not mean the number of ELEMENT nodes that have attributes, but we actually mean the number of attribute=value definitions that appear in the document.
• When I try to use the dictionary XML file to test my program, I get:
  "Exception in thread 'main' java.lang.OutOfMemoryError : Java heap space". How can I solve this problem?
  You can increase the java heap size by using the -Xmx command line. In general:

  java -Xms<initial heap size> -Xmx<maximum heap size>

  The Defaults are:

  java -Xms32m -Xmx128m

  So, try running your program with

  java -Xmx512m ...

  That should hopefully give you enough heap size. (btw, our reference implementation does run on the dictionary file without heap space problem. So, you might have been too wasteful with memory; maybe you are using more recursion than necessary?!)
  It is OK if your program needs, say -Xmx512m, in order to handle the large dictionary file. But if you need more than 512m, then there is definitely something wrong with your program (and you won't get maximum points then).

• I will work from home; how can I submit the assignment?
  You have to transfer your source file to a machine at CSE (for instance, using the "scp" command). The you should log into a CSE machine (for instance, using the "ssh" command); from there (in the directory where you have the file you want to submit) do

  give cs4317 ass1 <yourfile>

  This will submit your file to the course account.