My apologies for the title wording, it was hard to explain in words. What I am trying to do I this:

I have a .txt file that has

cheese cracker salt 
bread butter ham

I want the user to be able to enter 'cheese' then type in pepper which will in turn update the file to become

cheese cracker pepper
bread butter ham

I am unsure how to go about editing the third word after I have the user input the first word.

CodePudding user response：

Your algorithm could look like this:

1. read in the file
2. split it up by spaces (you will get an array)
3. put the result into a modifiable list (you can't easily insert into an array)
4. search for the index of a word
5. insert another entry by index (you can calculate the correct index from the result of step 4)
6. overwrite the file with the contents of the list, separated by additional spaces.

CodePudding user response：

Here is a solution utilizing File module along with BufferedReader/BufferedWriter

packages

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.List;
import java.util.Scanner;
import java.nio.file.*;

Driver program

public class Main{
    public static void main(String[] args) throws IOException{
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the file name: ");
        String path = sc.nextLine();
        Path p = Paths.get(path);
        List <String> lines = Files.readAllLines(p);
        System.out.println("Enter new word:");
        String newWord = sc.nextLine();
        System.out.println("Which word would you like "   newWord   " to replace?");
        String oldWord = sc.nextLine();
        for(int i = 0; i < lines.size(); i  ){
            String line = lines.get(i);
            line = line.replace(oldWord, word); // if current word is old word, replace with new one
            lines.set(i, line); // update list
        }
        readFile(path); // read here will output original list
        writeListToFile(lines, path); // overwrite sample.txt file
        readFile(path); // read here will output updated text file from path
        sc.close();
    }

helper functions

    public static void readFile(String fileName){
        try{
            FileReader fr = new FileReader(fileName);
            BufferedReader br = new BufferedReader(fr);
            String line = br.readLine();
            while(line != null){
                System.out.println(line);
                line = br.readLine();
            }
            br.close();
        }catch(IOException e){
            System.out.println("Error reading file");
        }
    }

    public static void writeListToFile(List<String> list, String path){
        try{
            FileWriter fw = new FileWriter(path);
            BufferedWriter bw = new BufferedWriter(fw);
            for(int i = 0; i < list.size(); i  ){
                bw.write(list.get(i));
                bw.newLine();
            }
            bw.close();
        }catch(IOException e){
            System.out.println("Error writing to file");
        }
    }
}