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FileNotFoundException for a valid file using FileInputStream

When I write an FileInputStream, while I have the valid file, it throws a FileNotFoundException.
I used this:
package io;
import java.io.*;
public class implementIo {
public static int i;
public static FileOutputStream output;
public static FileInputStream input;
public static void main(String args[]) {
try {
output = new FileOutputStream("writeModification.txt");
input = new FileInputStream("modification.txt");
do {
i = input.read();
if(i != -1) output.write(i);
}while(i != -1);
} catch (Exception e) {
System.out.println("Exception caught " + e);
} finally {
try {
if(output == null) input.close();
}catch(IOException e) {
System.out.println("IOException caught: " + e);
}
}
}
}
While I had a two separate files named "modification.txt" and "printModification.txt" in the same package folder, yet the system threw a FileNotFoundException. Please help!

This is because the FileInputStream doesn't provide the file creation during initialization like new FileOutputStream() does. So if these have been said, we can see one interesting thing to keep in mind: the modification.txt will be created every time when you initialize the FileOutputStream (and won't be overwritten) and this is why most probably your code breaks at the new FileInputStream() line.
How can you handle your exception?
You either create your file before executing the code( manually with New -> Text Document etc. ) or modify your code and make use of File class :
File file = new File("modification.txt");
try {
file.createNewFile();
input = new FileInputStream(file);
//your code here - output etc.
Your code still doesn't work even if you have the files created in the same package folder? It's because the default path that your streams are looking for your files is the current working directory. Here is an example :
myproject
|___src
| |___main
| |___java
| |___io
| |___implementIo
|___writeModification.txt
|___modification.txt
This is the correct structure if you want to use the streams like you did (with just a simple file name in stream constructor argument). But if your files are not there, you have to specify the absolute path. Here is an example :
myproject
|___src
|___main
|___java
|___io
|___implementIo
|___writeModification.txt
|___modification.txt
And the correct way to access the files is this:
FileInputStream input = new FileInputStream("C://myproject//src//main//java//io//modification.txt");
Same for the output stream. (Please modify the path with your correct file location)

URI not hierarchical need to use File class for a method

I need to open a video file with my code, and it works perfectly fine in Eclipse but when I export into a runnable JAR, i get an error "URI not hierarchical".
I have seen people suggest using getResourceAsStream(), but i need to have a file object as i am using Desktop.getDesktop.open(File). Can anyone help me out?
Here is the code:
try {
URI path1 = getClass().getResource("/videos/tutorialVid1.mp4").toURI();
File f = new File(path1);
Desktop.getDesktop().open(f);
} catch (Exception e) {
e.printStackTrace();
}
if it helps my folder list is like
Src
videos
videoFile.mp4
EDIT:
I plan to run this on windows only, and use launch4j to create an exe.

You can copy the file from the jar to a temporary file and open that.
Here's a method to create a temporary file for a given jar resource:
public static File createTempFile(String path) {
String[] parts = path.split("/");
File f = File.createTempFile(parts[parts.length - 1], ".tmp");
f.deleteOnExit();
try (Inputstream in = getClass().getResourceAsStream(path)) {
Files.copy(in, f.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
return f;
}
And here's an example of how you'd use it:
Desktop.getDesktop().open(createTempFile("/videos/tutorialVid1.mp4"));

Java read file within static method, using ClassLoader gives FileNotFoundException

I want to read a file in my java class. My question is similar to this one, but there are two differences. first, I use a different project layout:
/src/com/company/project
/resources
In the resources folder I have a file called "test.txt":
/resources/test.txt
In the project folder I have a class test.java
/src/com/company/project/test.java
I want mu java class to be able to read the contents of test.txt in a STATIC METHOD. I've tried the following:
private static String parseFile()
{
try
{
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
String fileURL = classLoader.getResource("test.txt").getFile();
File file = new File(fileURL);
...
}
}
and the following paths:
File file1 = new File("test.txt");
File file2 = new File("/test.txt");
File file3 = new File("/resources/test.txt");
But they all throw a FileNotFoundException when I want to read the file. How can I correctly declare the path to my file in the snippet above with respect to my project setup and the fact that the method needs to be static?

You should use the class loader of the class which is in the same JAR as the resource instead of the TCCL. And then you need to specify the name of the resource with a full path. And it is typically not good to access those as files. Just open it directly for read (or copy it to a temp file if you need to):
InputStream is =
Project.class.getClassLoader().getResourceAsStream("/resource/test.txt");
BTW: if you simply want to open a file, you need to use a relative file name. This is searched relative to the start dir, which is normally the project main dir (in eclipse):
File resource = new File("resource/test.txt");
(but this wont work if you package it up as a JAR).

After endless trials, I gave up on ClassLoader and getResource methods of any kind.
Absolutely nothing worked, especially if the opening attempt was made from another project. I always ended up getting the bin folder instead of the src folder.
So I devised the following work around:
public class IOAccessory {
public static String getProjectDir() {
try {
Class<?> callingClass = Class.forName(Thread.currentThread().getStackTrace()[2].getClassName());
URL url = callingClass.getProtectionDomain().getCodeSource().getLocation();
URI parentDir = url.toURI().resolve("..");
return parentDir.getPath();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (URISyntaxException e) {
e.printStackTrace();
}
return "";
}
}
The getProjectDir method returns the physical path of the project from which it was called, e.g. C:/workspace/MyProject/.
After that, all you need to do is concatenate the relative path in MyProject of your resource file to open the stream:
public void openResource() throws IOException {
InputStream stream = null;
String projectDir = IOAccessory.getProjectDir();
String filePath = "resources/test.txt";
try {
stream = new FileInputStream(projectDir + filePath);
open(stream);
} catch(Exception e) {
e.printStackTrace();
} finally {
if (stream != null)
stream.close();
}
}
This technique works whether the openResource method is static or non-static, and whether it is called from within the project or from another project on the build path.

It really depends on how your IDE generates output from your project. Typically, classloaders load resources relative to the invoking classes, but if treated right, 'resources' will just end up in the 'root' of your output folder hierarchy, and you can access them accordingly.
For example, if I recreate your code in IntelliJ IDEA, in a class called com/acme/TestClass.class, the following output structure is generated within the IDE when building. This assumes I have "test.txt" sitting in a folder I called "resources", and that folder is specified as being a "resources root":
/com
/acme
TestClass.class
test.txt
The text file ends up in the output folder's root, so accessing it is simple. The following code works for me when I attempt to load the file in a static method within TestClass:
ClassLoader cl = TestClass.class.getClassLoader();
InputStream is = cl.getResourceAsStream("test.txt");

The only thing not covered in the other answers is that your URL conversion to file might not work correctly. If the directories above your project contain a characters that must be decoded then your call to 'getResource("test.txt").getFile()' is not giving you a valid java.io.File path.

I load shader for openGL ES from static function.
Remember you must use lower case for your file and directory name, or else the operation will be failed
public class MyGLRenderer implements GLSurfaceView.Renderer {
...
public static int loadShader() {
// Read file as input stream
InputStream inputStream = MyGLRenderer.class.getResourceAsStream("/res/raw/vertex_shader.txt");
// Convert input stream to string
Scanner s = new Scanner(inputStream).useDelimiter("\\A");
String shaderCode = s.hasNext() ? s.next() : "";
}
...
}
Another method to convert input stream to string.
byte[] bytes;
String shaderCode = "";
try {
bytes = new byte[inputStream.available()];
inputStream.read(bytes);
shaderCode = new String(bytes);
}
catch (IOException e) {
e.printStackTrace();
}

Properties setting via Servlet

I want to set data from configures.properties via servlet. configures.properties is locating in WEB-INF/classes. This is how I'm getting data:
public static String getDbPassword() {
Properties prop = new Properties();
try {
// load a properties file
InputStream in = Configures.class.getResourceAsStream(INPUT_FILE);
prop.load(in);
// get the property value
return prop.getProperty("dbPassword");
} catch (IOException ex) {
ex.printStackTrace();
}
return null;
}
But how to set? This is how I did:
public static void setDbPassword(String str) {
Properties prop = new Properties();
try {
//load a properties file
InputStream in = Configures.class.getResourceAsStream(INPUT_FILE);
prop.load(in);
prop.setProperty("dbPassword", str);
prop.store(new FileOutputStream(INPUT_FILE), null);
} catch (IOException ex) {
ex.printStackTrace();
}
}
But I'm catching java.io.FileNotFoundException after this. I think it happens after prop.store(new FileOutputStream(INPUT_FILE), null);. How should I modify OutputStream?
UPD:
This is how INPUT_FILE looks:
private static final String INPUT_FILE = "/config.properties";

Your INPUT_FILE is a resource path which getResourceAsStream will resolve relative to the classpath, but you're then trying to pass the same string to the FileOutputStream constructor which will try and treat it as an absolute path relative to the root of the filesystem. These are two different locations.
You could use ServletContext.getRealPath("WEB-INF/classes" + INPUT_FILE) to get the path you need for the FileOutputStream.
But the higher level issue here is that you shouldn't assume that your web application will have write access to its WEB-INF, or even that the directory exists on disk at all (e.g. if the app is running directly from a WAR rather than a directory unpacked on disk). If you want to store configuration data that can change then it should go in a file at a known location outside the web app (the location of this file could be an init parameter) where you know you will have read and write permission. This also stops your changes being overwritten when you deploy a new version of the app.

URL url = Configures.class.getResource(INPUT_FILE);
File file = new File(url.toURI());
OutputStream outputStream = new FileOutputStream(file);
...
prop.store(outputStream, null);

Try a FileWriter instead:
Writer writer = new FileWriter(INPUT_FILE);
...
prop.store(writer, null);

Can you try the following:
While reading the file
URL url = classLoader.getResource(INPUT_FILE);
InputStream in = url.openStream();
While writing :
new FileOutputStream(url.toURI().getPath())

Any files in your webapp should be considered read only. If you want mutable data you should use a database or some other data store.
J2EE advises against manipulating local files as it raises issues of clustering, transactions and security among other things.

How to read from a file not in Eclipse in Java

I have a file which is needed for running tests - this file needs to be personalized (name and password) by whomever is running the test. I do not want to store this file in Eclipse (since it would need to be changed by whomever runs the test; also it would be storing personal info in the repo), so I have it in my home folder (/home/conrad/ssl.properties). How can I point my program to this file?
I've tried:
InputStream sslConfigStream = MyClass.class
.getClassLoader()
.getResourceAsStream("/home/" + name + "/ssl.properties");
I've also tried:
MyClass.class.getClassLoader();
InputStream sslConfigStream = ClassLoader
.getSystemResourceAsStream("/home/" + name + "/ssl.properties");
Both of these give me a RuntimeException because the sslConfigStream is null. Any help is appreciated!

Use a FileInputStream to read data from a file. The constructor takes a string path (or a File object, which encapsulates string path).
Note 1: A "resource" is a file which is in the classpath (alongside your java/class files). Since you don't want to store your file as a resource because you don't want it in your repo, ClassLoader.getSystemResourceAsStream() is not what you want.
Note 2: You should use a cross-platform way of getting a file in a home directory, as follows:
File homeDir = new File(System.getProperty("user.home"));
File propertiesFile = new File(homeDir, "ssl.properties");

InputStream sslConfigStream = new FileInputStream("/home/" + name + "/ssl.properties")

You can simplify your work, using Java's 7 method:
public static void main(String[] args) {
String fileName = "/path/to/your/file/ssl.properties";
try {
List<String> lines = Files.readAllLines(Paths.get(fileName),
Charset.defaultCharset());
for (String line : lines) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
You can also improve your way of reading properties file, using Properties class and forget about reading and parsing your .properties file:
http://www.mkyong.com/java/java-properties-file-examples/

Is this a graphics program (ie. using the Swing library)? If so it is a pretty simple task of using a JFileChooser.
http://docs.oracle.com/javase/6/docs/api/javax/swing/JFileChooser.html
JFileChooser f = new JFileChooser();
int rval = f.showOpenDialog(this);
if (rval == JFileChooser.APPROVE_OPTION) {
// Do something with file called f
}

You can also use Scanner to read the file.
String fileContent = "";
try {
Scanner scan = new Scanner(
new File( System.getProperty("user.home")+"/ssl.properties" ));
while(scan.hasNextLine()) {
fileContent += scan.nextLine();
}
scan.close();
} catch(FileNotFoundException e) {
}