Delete specific line from text file-CodePudding

I want to have a method that will take the file path and then delete a specific line from a text file and this is the code I came up with.

Method.java

public class Method {
static void deletefileline(String file, Integer line) throws IOException {
    ArrayList<String> filecontent = new ArrayList<String>();
    try {
        File myObj = new File(file);
        Scanner myReader = new Scanner(myObj);
        while (myReader.hasNextLine()) {
            String data = myReader.nextLine();
            filecontent.add(data);
        }
        myReader.close();
    } catch (FileNotFoundException e) {
        System.out.println("An error occurred.");
        e.printStackTrace();
    }
    File f = new File(file);
    f.delete();
    filecontent.remove(line);
    try {
        File newfile = new File(file);
        newfile.createNewFile();
    } catch (IOException e) {
        System.out.println("An Error Occured");
    }
    for (Integer i = 0; i < filecontent.size(); i  ) {
        String textToAppend = "\r\n"   filecontent.get(i);
        Path path = Paths.get(file);
        Files.write(path, textToAppend.getBytes(), StandardOpenOption.APPEND);
    }
}

public static void main(String[] args) {
    deletefileline("src/test.txt", 1);
 }
}

This is the text file

test.txt

hi
hello
hii
helloo

This is the text file after i ran Methods.java

Output:

hi
hello
hii
helloo

It won't show it but at the first "hi" before that there is a space so it only added a space at line 1.

So the problem is that when it is running it only adds an extra line at line 1.

CodePudding user response：

Why is not the line removed?

https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html

E remove(int index) Removes the element at the specified position in this list.

boolean remove(Object o) Removes the first occurrence of the specified element from this list, if it is present.

Since Integer line is Object and not a primitive data type int, this call

filecontent.remove(line);

tries to remove the line with a content equal to new Integer(1).

Change the method argument to int line or add type cast to the call filecontent.remove((int) line).

Why is an empty line added?

The extra space is added by this statement:

String textToAppend = "\r\n"   filecontent.get(i);

Change it like this:

String textToAppend = filecontent.get(i)   "\r\n";

CodePudding user response：

This is a small snippet to perform same function as mentioned in question (kotlin version, however same can be done in java)

import java.io.File
class RemoveFileContent {
    fun deleteContentAtIndex(filePath: String, indexPos: Int) {
        val bufferedWriter = File("/SampleOutputFile.txt").bufferedWriter()
        File(filePath).readLines().filterIndexed { i, _ -> i != indexPos }.forEach {
            bufferedWriter.appendLine(it)
        }
        bufferedWriter.flush()
    }
}
fun main(args : Array<String>) {
    RemoveFileContent().deleteContentAtIndex("/SampleFile.txt",2)
}

Input :             Output:
    hi                  hi
    hello               hello
    hii                 helloo
    helloo

Disclaimer : Note that if your file content are huge, this can lead to high memory consumption, as stated here - How to remove first line of a text file in java