CodeGym/Help with Java Tasks/Ran it on a few test files and it seemed fine

Level 23

Szekesfehervar

14.10.2021
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8comments

Ran it on a few test files and it seemed fine

Question about the task

Long words

Java Core, Level 9, Lesson 11

Resolved

Maybe it's too late here (01:17) and I can't see the problem...

The main method's first parameter is file1 and the second is file2.
file1 contains words separated by spaces.
Write to file2 a comma-separated list of words longer than 6 characters.
file2 should not end with a comma.
Close the streams.

Example output to file2:
lengthy,shortened,abbreviation

Requirements:

The program must NOT read data from the console.
The program must read the first file's contents (use the FileReader constructor with a String parameter).
The file input stream (FileReader) must be closed.
The program should write to the second file all the words from the first file longer than 6 characters, separated by commas (use FileWriter).
The file output stream (FileWriter) must be closed.

package com.codegym.task.task19.task1925; /* Long words */ import java.io.*; public class Solution { public static void main(String[] args) throws Exception { // args = new String[] {"/uploads/teszt.txt", "/myfiles/outputfile.txt"}; BufferedReader bfr = new BufferedReader(new FileReader(args[0])); FileWriter fWr = new FileWriter(args[1]); String[] line = null; int linesCount = 0; while (bfr.ready()) { line = bfr.readLine().split(" ") ; for (int i=0; i<line.length; i++) { if ((i>0 || linesCount > 0) && line[i].length()>6) fWr.append(","); if (line[i].length()>6) fWr.append(line[i]); } linesCount++; } bfr.close(); fWr.close(); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

15 October 2021, 01:22

useful

When you are building an output where you need to add a delimiter, such as the comma in this task, I like to start by writing the first part by itself and then starting each additional part with the delimiter. So, it would look like this:

if(!br.ready()) return; // no lines in file, just end program
int i = 0;
String[] line = br.readline().split(" ");

// this bit of code will continue reading lines until it finds the first
// word that is greater than length 6, when it does it breaks the loop
// and moves to the next section. Otherwise, if no words greater than 6
// are found then the program ends
outer:
while (true) {
   for(; i < line.length; i++)
      if (line[i].length() > 6)
         break outer;
   if(!br.ready()) return; // end if no more lines, if this line is reached then no words were found
   line = br.readline().split(" ");
   i = 0;
}

// write the first part
fWr.write(line[i++]); // increase i

// then write all additional parts starting with the delimiter
while(true) {
   for(; i < line.length; i++)
      if (line[i].length() > 6)
         fWr.write("," + line[i]);

   if(!br.ready()) break;
   line = br.readline().split(" ");
   i = 0;
}

This code doesn't require a flag value for the first value and then checking if that flag value has been activated (after the first writable word has been found) every single word.

Lisa

Level 41

15 October 2021, 07:13

useful

I'll usually do the same but the code must not become to complicated. Then I'd rather go for KISS, like:

List<String> lines = readToList(args[0]); // blocking IO as little as possible
List<String> wordsList = new ArrayList<>(); // holding words > 6

for (String line : lines)
    for (String word : line.split("\\s+"))
        if (word.length() > 6)
            wordsList.add(word);

String result = String.join(",", wordsList);

or just extend Gellerts code, add a comma after each finding and remove the last with a final substring call (instead of repeatedly calling if) or.... streams (here that example won't validate as it does not use a FileReader for input. Youd first need to use a Reader to read the file into a list and stream from there.... then it's better to approach that differently)

try(FileWriter writer = new FileWriter(args[1])) {

    writer.write(Files.lines(Paths.get(args[0]), StandardCharsets.UTF_8)
            .flatMap(line -> Stream.of(line.split("\\s+")))
            .filter(word -> word.length() > 6)
            .collect(Collectors.joining(",")));
}

@Gellert, the problem you should see with such an input... test longWord

Gellert Varga

Level 23 , Szekesfehervar, Hungary

15 October 2021, 11:33

Lupe: I really like this tricky solution:)

Gellert Varga

Level 23 , Szekesfehervar, Hungary

15 October 2021, 11:34

Lisa: the String.join() method is very useful, I just came across it for the first time. I recommend it to everyone who reads this later.

Guadalupe Gagnon

Level 37 , Tampa, United States

15 October 2021, 13:52

Mine is not a "tricky" solution, both the while loops are identical excepting that the top one stops when the first word that fits the conditions to print is found, the next loop then prints every other word fitting the conditions starting with the delimiter. The way Lisa recommended to do it instead makes it less tricky, however the tradeoff is storing more data in the computers memory, which I figured you wanted to avoid. Everything in programming is a tradeoff: If you get greater speed efficiency you are probably losing memory efficiency; more concise code, such as using the Stream API, typically speeds up development while reducing bugs but the tradeoff is that efficiency of speed/memory always will be a bit higher then creating custom code from scratch. Me, personally, I like to challenge myself to find the fastest running solutions while using the least amount of "extra" memory as possible, not necessarily the shortest code. If being a developer is your main goal then I would recommend focusing on using the classes and API's that are designed to solve your problem (or each sub-problem) as much as possible. Employers will value you if you are able to create code fast and bug free. They will have higher level programmers on the payroll to optimize their projects after the fact.

Lisa

Level 41

15 October 2021, 14:26

Afaik the main purpose of Java is to create readable, easily understandable, maintainable and extendable code. If you need both, maintainable code and highly optimized code then Java offers the JNI for that. It lets you import C code. I don't want to say that you shouldn't take care of mem and cpu usage but the little penalties you have while using the (already optimized) Java apis (like the streams api) is negligible compared to the gained advantages (all the above). On the other hand we're still learning to code. And it is fun to optimize algorithms as far as possible. Just find your way... and have a look at the streams api. Once you understand it, you'll love it. Ahhh... writing, writing stories... why do I do that. I should go back to coding, the Restaurant is awaiting me... I hear it crying: finish me, finish me... add just a few more daemon threads, ahh.... I hear you, crazy, crazy... 😜🤪

Guadalupe Gagnon

Level 37 , Tampa, United States

15 October 2021, 14:48

I'm a hobbyist so I just do this as fun and a hobby. My goals are to create the fastest code I can. I will write tasks multiple times using different algorithms and/or classes, timing how fast the code runs. My initial idea was that the standard classes were highly optimized and should always be used, however that wasn't the case. The first time I realized this was using Math.pow() on one of the tasks. I literally sped up my code ~10-15% by writing my own pow(). I see the same results when I write my own code instead of using Streams.

Lisa

Level 41

15 October 2021, 14:55

All true... as said, everyone needs to find his or her way. And once you work for a company, you get precise guidelines on what the code should look like soon enough. Argh, again, writing again here...