Correct Output, But No Pass : /

Question about the task

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This is so aggravating after having spent so much time to just get the output correct. Anyone have any tips here? I've played around with the trailing spaces and nothng works.

Read 2 file names from the console.
Output to the second file all of the numbers from the first file.
Separate the numbers with a space.
Close the streams.

Example file content:
12 text var2 14 8v 1

Result:
12 14 1

Requirements:

The program should read file names from the console (use BufferedReader).
The BufferedReader used for reading input from the console must be closed after use.
The program must read the first file's contents (use the BufferedReader constructor that takes a FileReader argument).
The file input stream (BufferedReader) must be closed.
The program must write all of the numbers from the first file, separated by spaces, to the second file (use the BufferedWriter constructor that takes a FileWriter argument).
The file output stream (BufferedWriter) must be closed.

package com.codegym.task.task19.task1908; /* Picking out numbers Read 2 file names from the console. Output to the second file all of the numbers from the first file. Separate the numbers with a space. Close the streams. Example file content: 12 text var2 14 8v 1 Result: 12 14 1 Requirements: 3. The program must read the first file's contents (use the BufferedReader constructor that takes a FileReader argument). 4. The file input stream (BufferedReader) must be closed. 5. The program must write all of the numbers from the first file, separated by spaces, to the second file (use the BufferedWriter constructor that takes a FileWriter argument). 6. The file output stream (BufferedWriter) must be closed. */ import java.io.*; import java.util.ArrayList; public class Solution { public static void main(String[] args) throws IOException { //1. The program should read file names from the console (use BufferedReader). BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String fileInputName = reader.readLine(); String fileOutputName = reader.readLine(); BufferedReader fileReader = new BufferedReader(new FileReader(fileInputName)); //2. The BufferedReader used for reading input from the console must be closed after use. reader.close(); String line = null; while(fileReader.ready()){ line = fileReader.readLine(); } fileReader.close(); StringBuilder stringBuilder = new StringBuilder(); ArrayList<String> stringArrayList = new ArrayList<>(); for(int i = 0; i < line.length(); i++){ //if the current character is a digit and the next character isn't a space or a letter //If current char is Digit... if(Character.isDigit(line.charAt(i))){ //If next char is Digit, add it to your string. if(i == line.length() - 1) { stringBuilder.append(line.charAt(i)); stringArrayList.add(stringBuilder.toString()); break; }else if(Character.isDigit(line.charAt(i + 1))){ stringBuilder.append(line.charAt(i)); //If next character is letter or previous character is letter, reset the string. }else if(Character.isLetter(line.charAt(i + 1)) || Character.isLetter(line.charAt(i - 1))) { stringBuilder = new StringBuilder(); //If next character is a space, add current character to string, add string to arraylist, and reset. }else if (line.charAt(i + 1) == ' ') { stringBuilder.append(line.charAt(i)); stringArrayList.add(stringBuilder.toString()); stringBuilder = new StringBuilder(); } }else{ //Current character is not a digit. stringBuilder = new StringBuilder(); } } BufferedWriter fileWriter = new BufferedWriter(new FileWriter((fileOutputName))); for(int k = 0; k < stringArrayList.size(); k++){ if(k != stringArrayList.size() - 1){ fileWriter.write(stringArrayList.get(k) + " "); }else{ fileWriter.write(stringArrayList.get(k) + ""); } } fileWriter.flush(); fileWriter.close(); } }

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Thomas

Level 41 , Bayreuth, Germany

28 February 2023, 09:48

You read only the last line of the input file. Why don't you use a StringBuilder here too and separate the single lines with a space. This also simplifies things later. When I see that in a loop iteration the previous and/ or next index of an array is looked at, all alarm bells are ringing. You secured the next index, but not the previous one. The previous one is accessed when the char at the current index is a digit and char at i + 1 is not a letter (in the meaning of the Character.isLetter() method). A space is not a letter. $%&!")(/ are also no letters. Means "1 a" or "1%a" will throw an exception. - Avoid accessing previous or next indexes. - Avoid isLetter and isDigit as they may consider more characters to be a digit than you may think or less characters to be a letter than you may mean. This must not be a problem here. I have no clue how CG is doing the testing. - Instead keep it simple and just check if a char is a number with: if (c >= '0' && c <= '9') ... - Because you now added a space to the end of each line of the input file you can omit the end of string checking. Just doing all the logic when you find a space is enough. I'll show you below how I'd split words. I leave it to you to check whether a word is a number. When you finished the task you may want to look into regex as this makes things a lot easier. String.split() could also be a great help as it basically does what you actually are coding. The isNumber checking you already coded in tasks before (syntax quest afair).

Thomas

Level 41 , Bayreuth, Germany

28 February 2023, 09:50

solution

public static void main(String[] args) throws IOException {
    // make sure there is a trailing space or add a end of string check to the split method
    String line = "   12     text var2 14 8v 1 ";
    try (FileWriter out = new FileWriter("/tmp/eachWordInNewLine.txt")) {
        out.write(String.join("\n", split(line)));
    }
}

public static List<String> split(String s) {
    List<String> result = new ArrayList<>();
    StringBuilder sb = new StringBuilder();

    // loop over the string, because you do not need the index you can directly loop over the chars
    for (char c : s.toCharArray()) {
        // two cases here, if a space, create a word, if a letter, add it to the stringbuilder
        if (c == ' ') {
            if (sb.length() > 0)
                result.add(sb.toString());
            sb = setLength(0);
            continue;
        }

        sb.append(c);

        // enhance here with number checking use a boolean isNumber, only add to list if it is a number
    }
    return result;
}

not so good to understand but does not require a trailing space, again I leave filtering for numbers up to you, But in both versions it is not very difficult to add.

List<String> result = new ArrayList<>();
StringBuilder sb = new StringBuilder();

char[] c = s.toCharArray();
for (int i = -1; i < c.length;) {
    while (++i != c.length && c[i] != ' ') {
        sb.append(c[i]);
    }
    result.add(sb.toString());
    sb.setLength(0);
}
return result;

Mike S

Level 28 , Saint Louis, United States

6 March 2023, 18:39

Thank you so much, Thomas, for helping me work through this. Finally had the chance to revisit this today and begrudgingly abandoned my own strategies for yours. Still learned a lot!

Thomas

Level 41 , Bayreuth, Germany

6 March 2023, 20:44

Glad it worked out for you and that it was helpful. I just wanted to add that you of course may access prev and next elements in a loop. It just depends on what you're going to do. You just need to make sure you do not access illegal indexes (e.g. when coding sort algorithms like bubble or selection sort). This solution is a very low level approach and as said I'd go for a higher level one using either regex/ split or regex/ pattern-matcher. That way you could write a solution with just 4-5 lines but wouldn't have learned that much ;) Good luck