Struggling with this tak

Question about the task

Introducing tags

Java Core, Level 9, Lesson 11

Under discussion

Hi there, I've been struggling with this task for days and still I'm not able to get it validated. Any help, please?

Read from the console the name of a file containing HTML.

Example:
Info about Leela Leela Turanga
Supergirl

The main method's first parameter is a tag name. For example, "span".
Display all tags that match the specified tag.
The order should match their order in the file, each tag on a new line.
The number of spaces, newline characters (\n), or carriage returns (\r) does not affect the result.
The file does not have a CDATA tag. Each opening tag has a separate closing tag, and there are no self-closing tags.
Tags may have nested tags.

Example output:
Leela Turanga Leela Turanga Super girl

Tag templates:
<tag>text1</tag> <tag text2>text1</tag> <tag text2>text1</tag>

text1 and text2 can be empty

Requirements:

The program must read the file name from the console (use BufferedReader).
The BufferedReader used for reading input from the console must be closed after use.
The program must read the file's contents (use FileReader).
The file input stream (FileReader) must be closed.
The program must write to the console all the tags that match the tag specified by the argument passed to the main method.

package com.codegym.task.task19.task1918; /* Introducing tags */ import java.io.*; import java.util.ArrayList; import java.util.Collections; import java.util.List; public class Solution { public static void main(String[] args) { args = new String[]{"tag"}; // If there's no args the return if(args[0]==null){ return; } // Getting the file name String fileName = null; try(BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))){ while(fileName==null || fileName.isEmpty()) { fileName = reader.readLine(); } } catch (IOException e) { throw new RuntimeException(e); } // Reading the info from the file StringBuilder stringBuilder = new StringBuilder(); try(BufferedReader reader = new BufferedReader(new FileReader(fileName))){ // While there's info to be read, read it while(reader.ready()){ stringBuilder.append(reader.readLine()); } // If the file is empty then return if (stringBuilder.toString().isEmpty()) { return; } // Write to the console the result for(String str : Tags(stringBuilder.toString(), args[0])){ if(str!=null && !str.isEmpty()) { System.out.println(str); } } } catch (FileNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } } private static List<String> Tags(String string, String tag){ final String openingTag = "<" + tag; final String closingTag = "</".concat(tag).concat(">"); int pos = string.indexOf(openingTag); pos += openingTag.length(); List<String> tags = new ArrayList<>(); // Splitting the file content by the REGEX Collections.addAll(tags, string.substring(pos).split(openingTag)); int index = 0; // Adding the REGEX to the start of every tag while (index < tags.size()){ tags.set(index, openingTag.concat(tags.get(index))); index++; } // Searching for strings with non ending tags // When a string is found, the next element of the Tags list is added // Until an ending tag is found and there're the same number of opening and closing tags index = 0; while(index < tags.size()){ int addIndex = 1; while(!tags.get(index).endsWith(closingTag) || Collections.frequency(Collections.singleton(tags.get(index)),openingTag)!= Collections.frequency(Collections.singleton(tags.get(index)), closingTag)){ tags.set(index, tags.get(index).concat(tags.get(index + addIndex))); tags.remove(index + addIndex); } index++; } // Getting the inner tags index = 0; while(index < tags.size()){ int n = 1; if(CountTags(tags.get(index),openingTag)>1){ int posOpeningTag = tags.get(index).indexOf(openingTag); int posClosingTag = tags.get(index).lastIndexOf(closingTag); while(true){ if(posOpeningTag>0){ posOpeningTag = tags.get(index).indexOf(openingTag, posOpeningTag); if(posOpeningTag==-1){ break; } posClosingTag = tags.get(index).lastIndexOf(closingTag,posClosingTag); String innerStr = tags.get(index).substring(posOpeningTag, posClosingTag + closingTag.length()); tags.add((index + n), innerStr); n++; } posOpeningTag++; posClosingTag--; } } index+=n; } return tags; } //Counts how many tags are in a string private static int CountTags(String string, String tag){ int countTags = 0; String[] buffer = string.split(tag); for(String str : buffer){ countTags = (str!=null && !str.isEmpty())?countTags+=1: countTags; } return countTags; } }

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LuisRC

Level 39 , Gijón, Spain

16 April 2022, 20:11

Ok Lisa. Thanks for your help.

LuisRC

Level 39 , Gijón, Spain

16 April 2022, 15:16

Ok Lisa. I see that I have my solution too complicated even if it gets the solution. Thanks for your solutions. Mine didn't pass the validation so I try your first one. One question, why "part.split(startTag)" gives one of the splitting parts as an empty (" ") part?

Lisa L

Level 47 , Nuremberg, Germany

16 April 2022, 16:18

if the regex you use to split is at the beginning of the string (eg, regex = "@", string = "@hello"), then the result is a 2 element array. If the regex is at the end ("hello@") then the result is a 1 element array. So I just add a space ("hello@ ") and the splitting result gives a 2 element array as well. I use that to count start tags and end tags. If no of start tags == no of end tags (split array length), then we have a match and can output from start to end.

Lisa L

Level 47 , Nuremberg, Germany

16 April 2022, 13:43

Try to remove the while in line 24. Didn't this result in not validating already before? If that is not the problem I suspect your approach isn't validators darling. Maybe cause you cut out (split) parts of the original string and then readd that again. I wrote two approaches for that task and both give the same result as yours in my test. Contrary to your splitting I get the result using substring. The approach using pattern-matcher even works with using regex to get the entire start tag from < to > String startTag = "<" + search + ".*?>". The substring approach needs a fixed length

StringBuilder html = new StringBuilder();

String search = args[0];
String startTag = "<" + search;
String endTag = "</" + search + ">";

try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
     BufferedReader in = new BufferedReader(new FileReader(reader.readLine()))) {
    while (in.ready()) html.append(in.readLine());
} catch (IOException ignore) {}

// solution using patter-matcher
Matcher matcherStart = Pattern.compile(startTag).matcher(html);
Matcher matcherEnd = Pattern.compile(endTag).matcher(html);

while (matcherStart.find()) {
    int startPos = matcherStart.start();

    while (matcherEnd.find(startPos)) {
        String part = html.substring(matcherStart.start(), matcherEnd.end());
        if (part.split(startTag).length == (part + " ").split(endTag).length) {
            System.out.println(part);
            break;
        }
        startPos = matcherEnd.end();
    }
}

Lisa L

Level 47 , Nuremberg, Germany

16 April 2022, 13:44

// solution using substring
for (int counter = 0; counter <= html.length() - endTag.length() ; counter++) {
    int tagStartIndex;
    int nestedOccurrences = 0;

    if (html.substring(counter, counter + startTag.length()).equals(startTag)) {
        tagStartIndex = counter;
        counter += startTag.length();
        for (int endCounter = counter; endCounter <= html.length() - endTag.length(); endCounter++) {
            if (html.substring(endCounter, endCounter + startTag.length()).equals(startTag))
                nestedOccurrences++;
            if (html.substring(endCounter, endCounter + endTag.length()).equals(endTag)) {
                if (nestedOccurrences > 0) {
                    nestedOccurrences--;
                } else {
                    System.out.println(html.substring(tagStartIndex, endCounter + endTag.length()));
                    break;
                }
            }
        }
    }
}