Homework SourseSimple XML Checker Objective Write a program that checks whe
Simple XML Checker!
Objective:
Write a program that checks whether or not a given file is formatted correctly for a very simple version of XML. In this simple version of XML you have tags that denote information. Each tag has a “start-tag”, and an “end-tag”. The start-tag is denoted by a value enclosed by “< >”, and the end-tag similarly denoted by “”. Each start-tag must have an end-tag. Elements fall in between the start and end tags, and can also other tags can be nested in as well. In this version of XML you can assume that tags and elements will always be on separate lines, and no additional attributes (such as id = “3”>) will be a part.
Well formatted example
33
Another well formatted example
100
Not well formatted example
44
Another not well formatted example
33
To solve this problem you must:
Write a stack, and use it to solve this problem
You may NOT use the built-in java stack
You may either implement the stack as a linked structure or an array. If you use an array assume the max size is 100;
Write another class that has a main method which takes in a file name and checks whether or not that file is correctly formatted.
Here’s a basic idea:
If the next line is enclosed by “< >” with a tag in between, then push the tag onto the stack
If the next line is enclosed by “” with a tag in between, then
Pop one element off the stack
Check if that element matches with end-tag. If it does then continue on, but if it doesn’t then it is not formatted correctly
All other values and elements can be ignored
If by the end there are no tags left on the stack then it is properly formatted, but if the stack still has tags then it is not properly formatted.
Also the string methods “charAt(index)” and “substring(startIndex, endIndex)” may be very useful
Here are some files to test with
goodXML1
goodXML2
goodXML3
badXML1
badXML2
badXML3
Example Dialog:
Welcome to the simple XML tester. Time to test simple XML\'s
Enter a file name
goodXML1.txt
This XML File was formatted correctly
Another Example Dialog:
Welcome to the simple XML tester. Time to test simple XML\'s
Enter a file name
badXML1.txt
This XML file is not formatted correctly
The tag \"bad\" does not have a match
Yet Another Example Dialog:
Welcome to the simple XML tester. Time to test simple XML\'s
Enter a file name
badXML3.txt
This XML File was not formatted correctly
The following tags didn\'t have an end tag
super really bad
really bad
bad
Solution
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
public class XMLParser {
/**
* Opens and reads the given file and prints whether it has valid
* XML content or not
*
* @param filePath
*/
public void parseFile(String filePath) {
String inputText = new String();
try {
inputText = getText(filePath);
} catch (IOException e) {
e.printStackTrace();
}
if (isValidXML(inputText)) {
System.out.println(\"The given file is a valid XML file\");
return;
}
}
/**
* Reads the complete file and retuns it as a string
*
* @param filePath
* @return
* @throws IOException
*/
public String getText(String filePath) throws IOException {
String inputLine;
StringBuffer buffer = new StringBuffer();
BufferedReader inputReader = new BufferedReader(new FileReader(filePath));
while ((inputLine = inputReader.readLine()) != null) {
buffer.append(inputLine+\"\ \");
}
inputReader.close();
return buffer.toString();
}
/**
* Retuns whether the given XML text is a valid or not
* @param inputText
* @return
*/
public boolean isValidXML(String inputText) {
UserStack stack = new UserStack();
int i=0;
while (i<inputText.length()) {
if (inputText.charAt(i) == \'<\') {
/* Find out whether it is a start tag or end tag
*/
boolean isStartTag = true;
if (inputText.charAt(i+1) == \'/\') {
isStartTag = false;
i++;
}
int j = i+1;
/* Read the tag name
*/
StringBuffer tag = new StringBuffer();
while (inputText.charAt(j) != \'>\') {
tag.append(inputText.charAt(j));
j++;
}
i=j+1;
/* 1. push on the top of the stack, if it is a start tag
* 2. Otherwise pop an element from the stack and compare
*/
if (isStartTag) {
stack.push(tag.toString());
}
else {
String tos = stack.peek();
if (tos == null) {
System.out.println(\"The given file is not a valid XML file\ \");
return false;
}
if (tos.equals(tag.toString())) {
stack.pop();
}
else {
System.out.println(\"The given file is not a valid XML file\ \"
+ \"Following elements didn\'t had a tag : \");
stack.printStack();
return false;
}
}
}
else {
i++;
}
}
/*
* If the stack contains elements at the end
* then XML is invalid
*/
if (!stack.isEmpty()) {
System.out.println(\"The given file is not a valid XML file\ \"
+ \"Following elements didn\'t had a tag : \");
stack.printStack();
return false;
}
return true;
}
public static void main(String args[]) {
/* Take in the file name from the user
* */
Scanner inputScanner = new Scanner(System.in);
System.out.println(\"Enter a file name : \");
String fileName = \"/home/zubair/Desktop/\" + inputScanner.nextLine();
inputScanner.close();
/*
* Validate the content of the file
* */
XMLParser parser = new XMLParser();
parser.parseFile(fileName);
}
}
class UserStack {
private static final int MAX_CAPACITY = 100;
private String array[] = new String[MAX_CAPACITY];
private int top = -1;
public void push(String element) {
top++;
if (top < MAX_CAPACITY) {
array[top] = element;
return;
}
System.out.println(\"Stack is full, please remove some items\");
}
public String pop() {
if (top < 0) {
System.out.println(\"Stack is empty\");
return null;
}
return array[top--];
}
public String peek() {
if (top < 0) {
System.out.println(\"Stack is empty\");
return null;
}
return array[top];
}
public boolean isEmpty() {
if (top < 0) {
return true;
}
return false;
}
public int size() {
return (top + 1);
}
public void printStack() {
for (int i=0; i<=top; i++) {
System.out.println(array[i]);
}
System.out.println();
}
}
