I don't quite fully understant the requirements.

Question about the task

Under discussion

Here is what I have done. 1. I am reading the file and appending it to a string builder. 2.I am checking in a while loop is there is a beginning tag. 3.I create a substring from the beginning tag to the ending tag. 4. I check if there is another beginning tag in my substring in a while loop. 4.1 If there is not I am printing the substring. The new file content is the file content beginning from the first index of ending tag + it's length to the finish. 4.2. If there is , my substring is from the first beginning tag to the second beginning tag and I add the ending tag. The new file content is substring between last index of beginning tag and first index of ending tag plus the substring of the file from the last index of ending tag. Then I repeat. I admit that the algorithm works only if there are a maximum of 2 nested tags. Can I get some advice and some more inputs to test?

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.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader=new BufferedReader(new InputStreamReader(System.in)); String fileName= reader.readLine(); reader.close(); BufferedReader reader1=new BufferedReader(new FileReader(fileName)); StringBuilder builder=new StringBuilder(); String data; while((data= reader1.readLine())!=null){ builder.append(data+" "); } reader1.close(); String beginingTag="<"+args[0]; String endingTag="</"+args[0]+">"; String fileContent= builder.toString(); while(fileContent.contains(beginingTag)){ int firstIndexBeginingTad=fileContent.indexOf(beginingTag); int firstIndexEndingTag=fileContent.indexOf(endingTag); String tagsSubstrin=fileContent.substring(firstIndexBeginingTad,firstIndexEndingTag+endingTag.length()); if(tagsSubstrin.indexOf(beginingTag)==tagsSubstrin.lastIndexOf(beginingTag)){ System.out.println(tagsSubstrin); fileContent=fileContent.substring(firstIndexEndingTag+endingTag.length()); } else{ String tagsSubstring1=fileContent.substring(firstIndexBeginingTad,fileContent.lastIndexOf(beginingTag))+endingTag; System.out.println(tagsSubstring1); fileContent=fileContent.substring(fileContent.lastIndexOf(beginingTag),fileContent.indexOf(endingTag))+fileContent.substring(fileContent.lastIndexOf(endingTag)); } } } }

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catalin1989

Level 37 , Romania

22 November 2023, 09:55

I have tried the input from this https://codegym.cc/help/4890. and It worked.

Thomas

Level 41 , Bayreuth, Germany

22 November 2023, 14:07

I don't see how this can work? a) You take the first opening tag you find b) You take the last ending tag you find c) You intednd to create the substring from results a and b, but what if you have smth like <tag>contentA</tag><tag>contentB</tag> That makes your approach fail and you even won't have to look into some coding problems like line 44 (substring of last beggingTag to first ending tag... that'll fail often with an exception) All I can advise is to rethink the approach

catalin1989

Level 37 , Romania

23 November 2023, 11:26

So I took a new aproach. 1. I looked for the first index of the beginning tag and las index of the ending tag. This is the substring that I am working with. 2.I searched for all the indexes of the beginning tag and and the ending tag. 3. I added them all in an array and sorted them out. 4. I checked if the tag at index i is a begining tag. If yes I print the substring from index i to index i+1 plus the ending tag. The code looks like this: String beginingTag="<"+args[0]; String endingTag="</"+args[0]+">"; String fileContent= builder.toString(); String print=fileContent.substring(fileContent.indexOf(beginingTag),fileContent.lastIndexOf(endingTag)+endingTag.length()); ArrayList<Integer> list=new ArrayList<>(); ArrayList<Integer> list2=new ArrayList<>(); int beginningTagIndex=0; int endingTagIndex=0; while(true){ int index=print.indexOf(beginingTag,beginningTagIndex); beginningTagIndex=index+beginingTag.length(); list.add(index); if(index==print.lastIndexOf(beginingTag)){ break; } } while(true){ int index=print.indexOf(endingTag,endingTagIndex); endingTagIndex=index+endingTag.length(); list2.add(index); if(index==print.lastIndexOf(endingTag)){ break; } } int[] array=new int[list.size()+ list2.size()]; for(int i=0;i< array.length/2;i++){ array[i]= list.get(i); array[i+list2.size()]=list2.get(i); } Arrays.sort(array); for(int i=0;i<array.length-1;i++){ int jump=array[i]-beginingTag.length(); String forPrinting=print.substring(array[i],array[i+1])+endingTag; if(print.indexOf(beginingTag, jump )==array[i]){ System.out.println(forPrinting); } } }

Thomas

Level 41 , Bayreuth, Germany

23 November 2023, 14:52

A lot of the easy approaches have problems. That one I liked a lot till I more thoroughly tested it

// !!!! not working code
String
        tag = "t",
        html = """
                <t>1<t>2</t>3<t>4</t>5</t>    <t>6</t>
                """.replaceAll("\n", ""), // not sure if one needs to replace using "" or " "


        startTag = "<" + tag + ".*?>",
        endTag = "</" + tag + ">";

Matcher matcherStart = Pattern.compile(startTag).matcher(html);
Matcher matcherEnd = Pattern.compile(endTag).matcher(html);

List<Integer> startIndexes = new ArrayList<>();
List<Integer> endIndexes = new ArrayList<>();

while (matcherStart.find()) {
    startIndexes.add(matcherStart.start());
}

while (matcherEnd.find()) {
    endIndexes.add(matcherEnd.end());
}

while (!startIndexes.isEmpty()) {
    int
            count = 0,
            nestingDepth = -1,
            end = endIndexes.get(0);

    while (count < startIndexes.size() && startIndexes.get(count++) < end)
        nestingDepth++;

    System.out.println(html.substring(startIndexes.get(0), endIndexes.get(nestingDepth)));
    startIndexes.remove(0);
    endIndexes.remove(nestingDepth);
}

It works with the Leela example but the one I included makes it fail. Two lists with opening and closing tags. You get the first closing tags end index and count how many opening tags you have before that. If it is two, then you grab the 2nd closing tag. The problem is, if there is another opening tag after the first closing tag that approach will fail. You see that an lightweight nesting detection may lead to failure.

Thomas

Level 41 , Bayreuth, Germany

23 November 2023, 14:52

What you could try is: Get the first opening tag then advance in the string and count opening tags and closing tags you find. If you find an closing tag you compare count of opening and closing occurances. If they missmatch you continue further. That is not optimized but works.