I have the next code which has to open a File given by the user. The adress in which the file is located is correct, but the problem is that it keeps throwing the exception FileNotFoundException and i can´t figure out what the problem is.
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.RandomAccessFile;
public class OpenFile{
public static void main(String[] args) {
String fileName,name,r = "C:/Users/MyName/workspace/Proyect/";
Scanner t = new Scanner(System.in);
System.out.print("Give me the name of the file: ");
name = t.nextLine();
t.close();
fileName = r+name;
try
{
File f = new File(fileName);
RandomAccessFile ra = new RandomAccessFile(f,"r");
}
catch(FileNotFoundException ex)
{
System.out.println("cannot open file");
}
}
}
Couple Of Tips:
First, you should replace / this with File.separator
"CFile.separatorUsersFile.separatorMyNameFile.separatorworkspaceFile.separatorProyect`File.separator"
Second, your variables fileName and name are not intilized
it is better to define them like this.
String fileName ="";
String name=""; <------ which is more readable
Third it is good to put your scanner in try catch block with resources so there is not need to be close manualy like
try(Scanner input = new Scanner(System.in)){
}catch(FileNotFoundException e){
}
Hope these tips help you to solve your issue
Related
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.
I made this homework exercise to read text from a text file and store it reversed into another new file. This is the code:
import java.util.*;
import java.io.*;
public class FileEcho {
File file;
Scanner scanner;
String filename = "words.txt";
File file1 ;
PrintWriter pw ;
void echo() {
try {
String line;
file = new File( filename);
scanner = new Scanner( file );
file1 = new File("brabuhr.txt");
pw = new PrintWriter(file1);
while (scanner.hasNextLine()) {
line = scanner.nextLine();
String s = new StringBuilder(line).reverse().toString();
pw.println(s);
}
scanner.close();
} catch(FileNotFoundException e) {
System.out.println( "Could not find or open file <"+filename+">\n"+e
);
}
}
public static void main(String[] args) {
new FileEcho().echo();
}
}
and here is a picture Picture here
The question is: why is the newly generated file decreased in size despite having the same characters but reversed?
Would be great if someone can explain it because even my professor didn't know why is that.
P.S; the context of the file is just some words from the dictionary.
Also in other students computers so the problem is not from my computer
The problem is that you never closed the output stream pw, so that any pending output isn't written to the underlying file. This may cause truncation of your file.
You should have closed the output stream with pw.close() in a finally, or in a try with resources.
try (pw = new PrintWriter(file1)) {
while (scanner.hasNextLine()) {
line = scanner.nextLine();
String s = new StringBuilder(line).reverse().toString();
pw.println(s);
}
}
Your implementation can be simplified to be the following:
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
public class FileEcho {
void echo() throws IOException {
try (PrintWriter pw = new PrintWriter("brabuhr.txt")) {
Files.lines(Paths.get("words.txt"))
.map(s -> new StringBuilder(s).reverse().toString())
.forEach(pw::println);
}
}
public static void main(String[] args) throws IOException {
new FileEcho().echo();
}
}
In this example I used a 'try-with-resources' to have the PrintWriter pw autoclosed.
I am trying to read a .txt file and search for a word, but the program just closes with Process finished with exit code 0.
import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;
public class LogParser {
static Scanner file;
static ArrayList text = new ArrayList();
static String path = new String();
static String check = new String();
private static int a = 0;
static Scanner inpunt = new Scanner(System.in);
public static void main (String[] args) {
System.out.println("Input path to file");
path = inpunt.nextLine();
File texts = new File(path);
try {
file = new Scanner(new File(path));
} catch (Exception e) {
System.out.println("Can't open file");
}
try {
while (file.hasNext()) {
text.add(a, file.nextLine());
check = text.get(a).toString();
if (check.contains("cap"))
System.out.println("Allert!!!!!!!!!!!!!!!!!!!!!!!!!!!" + text.get(a));
a = a + 1;
}
} catch (Exception e) {
// System.out.println("Can't open file");
if (file.toString().contains("cap"))
System.out.println("cap" + "Path to file: " + path);
System.out.println(text.size());
}
}
}
The text in the .txt file is:
let's try read this cap
If I try to open an xml file, everything is ok. My problem is only in txt files.
As mentioned in the comments, your path variable isn't set. You're trying to create a new file and passing in a path that hasn't been instantiated.
I am trying to write code for a word guessing game, and it works well when I use bufferedreader and inputstream combined. But when I try it using scanner, it cannot find the file, even though in both instances the file is in the same folder. It is in a folder called res under the src folder in my project folder(I am coding in eclipse).
import java.util.ArrayList;
import java.util.Scanner;
import java.io.File;
public class WordGen {
private final String filename = "/res/words.txt";
File file = new File(filename);
Scanner input = null;
private ArrayList<String> list = new ArrayList<>();
public WordGen() {
try {
input = new Scanner(file);
while (input.hasNextLine()) {
String w = input.nextLine();
list.add(w);
}
} catch (Exception ex) {
System.out.println("File not found.");
}
}
public String getword() {
if (list.isEmpty()) {
return "NOTHING";
}
return list.get((int) (Math.random() * list.size()));
}
}
public class test {
public static void main(String[] args) {
WordGen wordgen = new WordGen();
System.out.println(wordgen.getword());
}
}
I tried searching for this problem but couldn't find it here. I am guessing it's a very small error which I cannot figure out. Thanks and regards.
EDIT: Here's the other code that worked(Everything else same as before):
public WordGenerator()
{
try(InputStream input = getClass().getResourceAsStream(fileName);
BufferedReader bfreader = new BufferedReader(new InputStreamReader(input)))
{
String line = "";
while ((line = bfreader.readLine()) != null)
words.add(line);
}
catch (Exception e)
{
System.out.println("Couldn't find file");
}
}
Scanner is trying to load a file - and you're providing an absolute filename, /res/words.txt.
In order to create an InputStream, you're loading a resource, giving it an absolute resource name, even though you've called the variable fileName:
getClass().getResourceAsStream(fileName)
That works because it can load a resource called /res/words.txt from the classpath, but it's not loading a file with a filename of /res/words.txt.
You could use a filename of res/words.txt, if you run the code from the src directory... or you could just stick to using getResourceAsStream, which is probably a better idea as it doesn't rely on your working directory, and will continue to work even if your code and resources are packaged up into a jar file.
If you really want to use Scanner, you could always use new Scanner(input) - there's a Scanner constructor accepting an InputStream.
I have most of it down but when I try to make the copy, no copy is made.
It finds the files in the specified directory like it is supposed to do and I think the copy function executes but there aren't any more files in the specified directory. Any help is appreciated. I made a printf function that isn't shown here. Thanks!
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.ArrayList;
import java.util.Scanner;
import org.apache.commons.io.FilenameUtils;
import org.apache.commons.io.FileUtils;
import static java.nio.file.StandardCopyOption.*;
public class Stuff {
static String path, oldExtn, newExtn;
static Boolean delOrig = false;
private static void getPathStuff() {
printf("Please enter the desired path\n");
Scanner in = new Scanner(System.in);
path = in.next();
printf("Now enter the file extension to replace\n");
oldExtn = in.next();
printf("Now enter the file extension to replace with\n");
newExtn = in.next();
in.close();
}
public static void main(String[] args) {
getPathStuff();
File folder = new File(path);
printf("folder = %s\n", folder.getPath());
for (final File fileEntry : folder.listFiles()) {
if (fileEntry.getName().endsWith(oldExtn)) {
printf(fileEntry.getName() + "\n");
File newFile = new File(FilenameUtils.getBaseName(fileEntry
.getName() + newExtn));
try {
printf("fileEntry = %s\n", fileEntry.toPath().toString());
Files.copy(fileEntry.toPath(), newFile.toPath(),
REPLACE_EXISTING);
} catch (IOException e) {
System.err.printf("Exception");
}
}
}
}
}`
The problem is that the new file is created without a full path (only the file name). So your new file is created - only not where you expect...
You can see that it'll work if you'll replace:
File newFile = new File(FilenameUtils.getBaseName(fileEntry
.getName() + newExtn));
with:
File newFile = new File(fileEntry.getAbsolutePath()
.substring(0,
fileEntry.getAbsolutePath()
.lastIndexOf(".")+1) + newExtn);