Need help

Question about the task

Finding data inside a file

Java Core, Level 8, Lesson 11

Under discussion

Need help.

Read a file name from the console.
Search the file for information related to the specified id. Display it in the format used in the file.
The program is started with one argument: id (an int).
Close the streams.

The file data is separated by spaces and stored in the following order:
id productName price quantity
where id is an int
productName is a String — it can contain spaces
price is a double
quantity is an int

The information for each product is stored on a separate line.

Requirements:

The program should read a file name from the console.
Create an input stream for the file.
The program should search the file and display information related to the specified id passed as the first argument.
The stream used to read the file must be closed.

package com.codegym.task.task18.task1822; /* Finding data inside a file */ import java.io.BufferedReader; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStreamReader; public class Solution { public static void main(String[] args) throws IOException { int id = Integer.parseInt(args[0]); // int id = 5; // Read a file name from the console. BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String fileName = reader.readLine(); // String fileName = "f3.txt"; reader.close(); FileInputStream fis = new FileInputStream(fileName); char c; String line = ""; while (fis.available() > 0) { line += (char)fis.read(); if(line.contains("\n")) { if(line.startsWith(Integer.toString(id))){ System.out.println(line); break; } else { line = ""; } } } fis.close(); } }

Comments (1)

Popular
New
Old

You must be signed in to leave a comment

Guadalupe Gagnon

Level 37 , Tampa, United States

27 November 2019, 14:29

When using streams It is a lot more efficient and easier if you read in all the data (or large chunks until all the data is complete). You can accomplish this with a buffer by removing the while loop and replacing with this:

// creates a buffer and sets it to the size of the file, this will read in ALL at once
byte[] buffer = new byte[fis.available()];
// the read method can take a 'byte[]' and will fill it with data until it is full
fis.read(buffer);
// use the string constructor and it will convert all those bytes into chars for you
String data = new String(buffer).replaceAll("\r", "");
// remove all the carriage returns

// split the file into clean individual lines
String[] lines = data.split("\n");

This code will read all the data in the file in one shot, .available() method returns the amount of unread bytes and since we haven't read any at this point, total bytes is what it returns. Use this in initiating the buffer size. For most tasks on codegym this works fine however in the real world files can be very large and your buffer might only want to read in a few megabytes at a time. Once all the bytes are stored in the buffer create a new string and pass the buffer into the constructor. The String class will convert those bytes into characters and you can work with it. You will want to get into the habit of removing carriage returns because some tasks have them and some do not. Either way they are always preceded by or follow a new line character. To complete the task you could search the String for the id and output using substring(), but it is a little easier to split the full data up into lines and then process them until the correct one is found (sort of like you do in the while loop of your code). A little tip. Converting id to an int (line 15) is redundant because you convert it back to a string at line 30 and never use it as an int.