file IO

[warm blade]

Hi i need some help, I am given a file path and need to open said file and write to it, if it doesnt exist I need to create and then write to it. How do I do this?

[silver iris]

<@&987246399047479336> please have a look, thanks.

[silver iris]

While you are waiting for getting help, here are some tips to improve your experience:

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[silver lily]

Using types in either java.io such as File and FileReader, or in java.nio using Files

[warm blade]

i get that but am confused on the diff

of opening a file and creating a file

to me they both seem to be

File x = new File(filePath);

[silver lily]

That doesnt open or create

There may not even be a file at that path. That's why File has an exists() method

To create a file at that path, you'd call create()

[pseudo cedar]

I wonder if there's a way to improve this code.

        //I am given a file path and need to open said file and write to it, if it doesnt exist I need to create and then write to it. How do I do this?
        try{
            deleteFile("test.txt", "test2.txt");
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }


    private static void solution(String file) throws Exception{
        File t  = new File(file);
        if (t.exists()){
            //do logic
            writeToFile(t);
        }else{
            t.createNewFile();
            writeToFile(t);
        }
    }
    private static void writeToFile(File f) throws Exception{
        FileWriter fr = new FileWriter(f);
        BufferedWriter bw = new BufferedWriter(fr);
        String str = "Hello my name is ilyase and I love to eat pancakes";
        bw.write(str);
        bw.close();
        fr.close();
    }

    private static void deleteFile(String... f){
        for (String str : f){
            File file = new File(str);
            if (file.exists()){
                file.delete();
                System.out.println("deleted the file here !");
            }
            else{
                System.out.println("this file is not here !");
            }
        }
    }

[silver iris]

Detected code, here are some useful tools:

Formatted code

public static void main(String[] args) {
  //I am given a file path and need to open said file and write to it, if it doesnt exist I need to create and then write to it. How do I do this?
  try {
    deleteFile("test.txt", "test2.txt");
  } catch (Exception e) {
    e.printStackTrace();
  }
}
private static void solution(String file) throws Exception {
  File t = new File(file);
  if (t.exists()) {
    //do logic
    writeToFile(t);
  }
  else {
    t.createNewFile();
    writeToFile(t);
  }
}
private static void writeToFile(File f) throws Exception {
  FileWriter fr = new FileWriter(f);
  BufferedWriter bw = new BufferedWriter(fr);
  String str = "Hello my name is ilyase and I love to eat pancakes";
  bw.write(str);
  bw.close();
  fr.close();
}
private static void deleteFile(String...f) {
  for (String str : f) {
    File file = new File(str);
    if (file.exists()) {
      file.delete();
      System.out.println("deleted the file here !");
    }
    else {
      System.out.println("this file is not here !");
    }
  }
}

[silver lily]

Improve in what way?

[silver iris]

File IO in Java should be done preferably with NIO (Java 7+), revolving around the classes Files and Path; and not with the old interface File, BufferedReader, FileReader and similar.

NIO is simple to use. The path to a file is represented using the Path class:

Path path = Path.of("myFile.txt");

All file operations can be found in the Files class:

// Reading
List<String> allLines = Files.readAllLines(path);
// or as a single string
String content = Files.readString(path);
// or with a stream
try (Stream<String> stream = Files.lines(path)) {
  stream.forEach(System.out::println);
}

// Writing
Files.write(path, lines);
// or as a single string
Files.writeString(path, "hello world");
// or with extra options
Files.writeString(path, "hello world",
  StandardOpenOption.WRITE,
  StandardOpenOption.CREATE,
  StandardOpenOption.APPEND);

If you need more control over the process, you can fallback to the old interface, but prefer using the bridge methods from NIO (Files.newBufferedReader, Files.newInputStream, path.toFile() and similar) to benefit from advantages such as correct encoding and better error detection.

Here is a simple example of how to read a file line-wise with the old interface

try (BufferedReader br = Files.newBufferedReader(path)) {
  String line;
  while ((line = br.readLine()) != null) {
    System.out.println(line);
  }
}

it is way more verbose than NIO but it gives more control.

You must not forget to close file handles, even in all exceptional cases. Closing a handle manually is very hard, which is why you should always use try-with-resources for this to let Java automatically close the handle for you:

try (SomeResource resource = ...) {
  ...
} // Automatically closed here, even in exceptional cases

Zabuzard • used /tag id: nio · Apr 5, 2023, 7:08 AM

[silver lily]

You could use br.lines().toList() instead of "the old way". Doesn't use NIO

Although NIO is definitely the way to go

[pseudo cedar]

what NIO stands for ?

[silver lily]

New IO