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How can I read a file from a path relative of my Main class in Java?

On the same directory of my Main.java file, I have a package/folder named database, and inside the database package I have a file named Data.txt.
This is my code of Main.java, but it is throwing this error:
java: exception java.io.FileNotFoundException
How can I get the file from a relative file? I'm used to web development, and usually something with a . dot like "./folder/file.txt" works.
import java.io.File;
import java.util.Scanner;
import java.io.FileNotFoundException;
public class Main {
public static void main(String[] args) {
readFile();
}
public static void readFile() {
File file = new File("./database/Data.txt");
Scanner scanner = new Scanner(file);
try {
while (scanner.hasNextLine()) {
int i = scanner.nextInt();
System.out.println(i);
}
scanner.close();
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}

You are not importing FileNotFoundException class. also, scanner statement throws the exception which should inside try. Solution is as below.
import java.io.File;
import java.util.Scanner;
import java.io.FileNotFoundException;
public class Main {
public static void main(String[] args) {
readFile();
}
public static void readFile() {
File file = new File("database/Data.txt");
try {
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
int i = scanner.nextInt();
System.out.println(i);
}
scanner.close();
}catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
Only check if those content can read using scanner or not. Content having int properly. otherwise it will throw java.util.InputMismatchException.

Are you working on a mac or windows system.
I am on windows and ".\database\Data.txt" would most probably work depending on where the file is in your file structure.

How to use relative filepath in java

Im trying to use relative path to read a file but the path cant be found.
maxSuccession is the name of my project
This is my workspace path: C:\Programming
This is my project's path C:\Programming\MaxSuccessions\maxSuccessions
This is my filepath C:\Programming\MaxSuccessions\Tests\test1\00.in.txt
package test1;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;
public class test1 {
public static void main(String[] args) throws IOException {
String myPath="..\\MaxSuccessions\\Tests\\test1\\";
Scanner sc = new Scanner(new File(myPath+"00.in.txt"));
System.out.println(sc.nextInt());
}
}

If your class file and required file are in the same directory, you can try this code:
public static void main(String[] args) {
String fileName = "00.in.txt"; //relative path from the path of your class.
try {
Scanner sc = new Scanner(Test.class.getResource(fileName).openStream());
System.out.println(sc.nextInt());
} catch (IOException e) {
e.printStackTrace();
}
}

How to load a csv in Java

I have a .csv file that I want to load in Java so that afterwards I will be able to work on it as on a normal matrix (array). Here you can see my code:
package MirMir;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Try1 {
public static void main(String[] args) throws FileNotFoundException
{
Scanner scanner = new Scanner(new File("/Users/Madalin/NetBeansProjects/imp fr/src/com/mkyong/util/Tracker.csv"));
scanner.useDelimiter(",");
while (scanner.hasNext())
{
System.out.print(scanner.next() + "|");
}
scanner.close();
}
}
The program runs perfectly without any errors, just the output I get in the end is: "BUILD SUCCESSFUL (total time: 0 seconds)" and that's all, without any data or anything.

Here is another way for this
public class Tracker {
public static void main(String[] args) throws FileNotFoundException, IOException
{
File f =new File("D:/Tracker.csv");
BufferedReader br = new BufferedReader(new FileReader(f));
String s ;
while ((s=br.readLine())!=null)
{
System.out.println(s);
}
br.close();
}
}
Well this might work ;)
P.S. Change the file location

The code is fine. No problem. I tested it on a sample csv file.
There seems to be some problem with your csv file.
Post a sample from your csv.

Error on finding file and on the New File location

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class running{
public static void main(String args[]) throws IOException {
double sum=0.0;
double num=0.0;
FileReader fin = (new File("running.txt");
Scanner src = new Scanner(fin);
while (src.hasNext()){
if(src.hasNextDouble()){
num=src.nextDouble();
sum=sum+num;
System.out.println(sum);
}else{
break;
}
}
fin.close();
}
}
Around the Scanner portion I cant seem to fix the error.
It says File cant be resolved to a type.
And the file cant be found.

You are missing an import java.io.File; statement. Since you did not import this class (and since your code is not located in the java.io package), Java can't recognize it.

You have a type in your code. You code should be:
FileReader fin = new FileReader(new File("running.txt"));
^^^^^^^^^^^^^^
You can't store instance of File within FileReader.
Also the error that you see is because you have not imported java.io.File, so you need to import File like:
import java.io.File;
A side note: You will need to handle FileNotFoundException.

Try importing java.io.File, and change your FileReader line to the following:
FileReader fin = new FileReader(new File("running.txt"));
It compiled fine for me.

Use the following code:
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
import java.io.File;
public class running{
public static void main(String args[]) throws IOException {
double sum=0.0;
double num=0.0;
FileReader fin = (new File("running.txt");
Scanner src = new Scanner(fin);
try{
while (src.hasNext()){
if(src.hasNextDouble()){
num=src.nextDouble();
sum=sum+num;
System.out.println(sum);
}else{
break;
}
}
}catch(Exception e){}finally{fin.close();}
}
}

geting a multiline text with scanner class in java

In a part of my university project I have to get a text with some lines then saving it in a string or a string array.My problem is that in scanner class using methods gets only one line of the input. So I cannot get the other lines.please help me.
public class Main {
public static void main(String[] args) {
java.util.Scanner a = new java.util.Scanner(System.in);
String b = "";
while (a.hasNextLine()) {
b += a.nextLine();
}
}
}

You can try to use isEmpty to detect an enter-only input.
UPDATED:
If your input also contain a blank line, then you may specify another terminator character(s); instead of only an empty string.
public class Main {
public static void main(String[] args) {
//for example ",,"; then the scanner will stop when you input ",,"
String TERMINATOR_STRING = ",,"
java.util.Scanner a = new java.util.Scanner(System.in);
StringBuilder b = new StringBuilder();
String strLine;
while (!(strLine = a.nextLine()).equals(TERMINATOR_STRING)) {
b.append(strLine);
}
}
}

If you are building your program from command line, then there's something called "input redirection" which you can use. Here's how it works:
Let's suppose your program is:
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class ScanningMultiline
{
public static void main (String[] args)
{
List<String> lines = new ArrayList<> ();
try (Scanner scanner = new Scanner (System.in))
{
while (scanner.hasNextLine ())
{
lines.add (scanner.nextLine ());
}
}
System.out.println ("Total lines: " + lines.size ());
}
}
Now suppose you have input for your program prepared in a file.
To compile the program you'd change the current directory of terminal/command prompt to the program directory and then write:
javac ScanningMultiline.java
And then to run, use input redirection like:
java ScanningMultiline < InputFile.txt
If your InputFile.txt is in another directory, just put its complete path instead like:
java ScanningMultiline < "/Users/Xyz/Desktop/InputFile.txt"
Another Approach
You can try reading your input directly from a file. Here's how that program would be written:
import java.io.IOException;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class ScanningMultiline
{
public static void main (String[] args)
{
final String inputFile = "/Users/Xyz/Desktop/InputFile.txt";
List<String> lines = new ArrayList<> ();
try (Scanner scanner = new Scanner (Paths.get (inputFile)))
{
while (scanner.hasNextLine ())
{
lines.add (scanner.nextLine ());
}
}
catch (IOException e)
{
e.printStackTrace ();
}
System.out.println ("Total lines: " + lines.size ());
}
}
This approach reads directly from a file and puts the lines from the file in a list of String.
Another Approach
You can read the lines from a file and store them in a list in a single line as well, as the following snippet demonstrates:
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
public class ScanningMultiline
{
public static void main (String[] args) throws IOException
{
final String inputFile = "/Users/Xyz/Desktop/InputFile.txt";
List<String> lines = Files.readAllLines (Paths.get (inputFile));
}
}
Yohanes Khosiawan has answered a different approach so I'm not writing that one here.