Develop Reference

Not able to access file on Local machine using Android even if the file is exist into the machine

I am trying to read file from the Local storage inside the Project of an Android.
However I am still having error like file not found exception. I had print the path of the file and I have checked with the browser file is there on the same path. but I am having still exception.
try {
File file = new File("D:\\Android SDK\\AndroidWorkspace\\Assignment4Test\\app\\src\\main\\assets\\studentnameid.txt");
if (file.exists()) {
System.out.println("File Is there ");
} else {
//It always executes the else blog.
file.createNewFile();
System.out.println(" file is not there so its creating Created File");
}
System.out.println(file.getAbsolutePath());
StringBuilder text = new StringBuilder();
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
text.append(line);
text.append('\n');
}
br.close();
} catch (Exception e) {
e.printStackTrace();
}
I would appreciate your help.
Thanks,
Krishna

D:\\Android SDK\\AndroidWorkspace\\Assignment4Test\\app\\src\\main\\assets\\studentnameid.txt is a path to a file on a Windows PC. Android is not Windows. You do not use Windows filesystem paths to refer to anything on Android.
My guess, based on that path, is that you have a file in your project in assets/. If so, use AssetManager (via getAssets() on a Context) and its open() method to access your asset. That will give you an InputStream to read from, directly or via an InputStreamReader.

to simplify this you have to use a localhost WAMP (for Windows ) or MAMP(for Mac), then store your file in the (www) folder, Go to android studio and set the link of your file like ( http://192.168.1.100/studentnameid.txt)
the 192.168.1.100 is your local IP address.
Not: you must change your IP address by the domaine name when you publish your app in Google play or other platforms

Writing foreign characters to .json file, eclipse vs jar

Using eclipse IDE to for tests on writing data to .json and .txt files with few foreign(Chinese, Hindi) characters using Java. I could successfully write into .txt where as .json displayed ascii characters.
Code Snippet:
try(BufferedWriter br = new BufferedWriter(new FileWriter(new File("test.json")))) {
JSONObject obj = new JSONObject();
obj.put("key", "Hello, ओ ो ु ऋ 样品");
String str = obj.toJSONString();
System.out.println(str);
br.write(str);
br.close();
} catch (Exception e) {
e.printStackTrace();
}
Output of .txt: {"key":"Hello, ओ ो ु ऋ 样品"}
Output of .json: {"key":"Hello, ओ ो � ऋ 样�"}
Have tried using DataOutputStream to write data. But the result is same.
On decoding, it worked to decode back as same foreign character and looks good.
On building a jar, and running the same as .jar file doesn't give same results. Writing and Reading both were displayed in ascii. Yes, I understand in eclipse the file is saved as utf-8, which helped to compile. By the way I'm using maven to build the jar.
Please help me with the wayout a solution. Thanks.

Selenium Chrome Driver In Tomcat is not working why?

was trying run my selenium automation code using java in a Tomcat server. It works fine when I run using javac but when it gets run on Tomcat as a jar It shows "com.google.common.base.Preconditions.checkState(ZLjava/lang/String;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)V|" this as a log. Here my selenium-chrome driver is placed in desktop of my local machine and path is defined (Tomcat is also a local server)

I would go with a buffered file reader like this:
public static void main(String[] args) throws IOException {
try {
File f = new File("data.txt");
BufferedReader b = new BufferedReader(new FileReader(f));
String readLine;
while ((readLine = b.readLine()) != null) {
if (readLine.contains("WORD"))
System.out.println("Found WORD in: " + readLine);
}
} catch (IOException e) {
e.printStackTrace();
}
}
where "WORD" is the word you are searching for.
The advantage of a BufferedReader is that it reads ahead to reduce the number of I/O roundtrips - or as they put it in the JavaDoc: "Reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines."
FileChannel is a slightly newer invention, arriving in the NIO with Java 1.4. It might perform better than the BufferedReader - but I also find it a lot more low-level in its API, so unless you have very special performance requirements, I would leave the readahead/buffering to BufferedReader and FileReader.
You can also say that BufferedReader is "line oriented" whereas FileChannel is "byte oriented".

I like the BufferedReader from Java.io with a FileReader most:
https://docs.oracle.com/javase/7/docs/api/java/io/FileReader.html
https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html
https://www.mkyong.com/java/how-to-read-file-from-java-bufferedreader-example/
It is easy to use and has most functions. But your file mus be char-based to use that ( like a text file)

Java: OutputStream to .exe Console App issue

I am trying to interact with a simple .exe I created from some Python code. I have tested the .exe through Windows cmd and it works just fine. When I try to send the same input to the .exe through my java program to produce the graphs I need, OutputStream just writes "error" to the console. I have tried sending a string and an integer through OutputStream but the same results are obtained no matter what. I have already interacted with X-Foil.exe, a console application use to produce airfoil data files, with great success through this same java app. As I have to preform curve fitting to the data, I used Python with the matplotlib plugin then used py2exe to create the .exe. I am trying to create a web application with the end goal of designing an aircraft wing, hence the use of java. Here is the method being use which I am having the problem with:
public void PyGrapher(String NACA_4d) {
try {
ProcessBuilder builder = new ProcessBuilder("PyAirfoilGraphing\\dist\\GraphPolars.exe");
builder.redirectErrorStream(true);
Process pr = builder.start();
OutputStream out = pr.getOutputStream();
BufferedReader in = new BufferedReader(new InputStreamReader(pr.getInputStream()));
double CL_alpha;
out.write((NACA_4d + "\n").getBytes());
System.out.println(in.readLine());
System.out.println(in.readLine());
System.out.println(in.readLine());
System.out.println(in.readLine());
//CL_alpha = Double.parseDouble(in.readLine());
pr.waitFor();
pr.destroy();
out.close();
in.close();
} catch (IOException | InterruptedException ex) {
}
}
Here is what I have read in from the console:
Input NACA 4-digit code: error
Traceback (most recent call last):
File "GraphPolars.py", line 16, in <module>
IOError: [Errno 2] No such file or directory: '..\\..\\AirfoilPolars\\NACA_0024.dat'
I am stumped, and have been for quite some time. There is not a problem with the python file, and it runs fine by itself in the current directory. Can anyone help, please?
-Nick K

Could it be something with relative paths? Python default path may not be picking up the local directory/file.
Did you try passing it the full windows path, 'C:\Foo\bar\AirFoil\... ' with properly escaped '\' characters?

How to read a file from remote system using java?

I have a file copied in one computer and I need to access the file from other computer.
I am not sure, which protocol or which technology to use for this?
Please provide me any hints for this..
Update:
I am using Ubuntu Linux system.
I used the code :
File f = new File("//192.168.1.157/home/renjith/picture.jpg");// 192.168.1.157 is the ip of the computer, where I have the picture file
Image image = ImageIO.read(f);
But it is giving an exception:
javax.imageio.IIOException: Can't read input file!
at javax.imageio.ImageIO.read(ImageIO.java:1275)
I have shared renjith folder also.

There are any number of ways to access files on remote machines, but they virtually all depend on the remote machine having been set up to provide the file in some way first. If you with to access files via java, the easiest method would probably be to set up an HTTP server on the remote machine (this can be done pretty easily using Apache HTTP server on a variety of platforms) and then using Apache Commons HTTPClient on the client side java app. Further discussion of how to install these or configure them is generally beyond the scope of Stack Overflow and would at least require a more specific question

HTTP is an option. However, if these are Windows machines on the same LAN, it would be easier to expose the directory on the remote machine via a file share and access the file through a regular file path. Similarly, if these are Unix-like machines, you could use regular file paths if you're using NFS. FTP's yet another option.

if the remote computer is in the same network and on a shared folder to the computer where your java code is running then try this piece of code for accessing it
File file = new File("\\\\Comp-1\\FileIO\\Stop.txt");
here Comp-1 is the DNS name of the machine containing the file in the network!!!

You might try:
URL url = new URL("file://192.168.1.157/home/renjith/picture.jpg");
Image image = ImageIO.read(url);

You could try to mount that path first, and then load it. Do a :
subst x: \\192.168.1.157
and then:
File f = new File("x:\\home\\renjith\\picture.jpg");
Image image = ImageIO.read(f)
It should work.

Share the directory and access the file thruogh java code
try this one:
File f = new File("//10.22.33.122/images")
File[] files = f.listFiles(new FilenameFilter() {
public boolean accept(File dir, String name) {
// Specify the extentions of files to be included.
return name.endsWith(".bmp") || name.endsWith(".gif");
}
});
// get names of the files
String[] fileNamesArray = null;
for (int indx = 0; indx < files.length(); indx++) {
fileNamesArray[indx] = files[indx].getName();
}
return fileNamesArray;

Map your IP to network drive and try let us say the drive letter is X,
then code changes to File f = new File("x:\\home\\renjith\\picture.jpg");
Infact your file is already loaded in object f , try priting the value of the path f.getAbsolutePath() to console and see.. Actual error is with ImageIO

You can read from remote and write to remote using jcifs-1.3.15.jar jar in java but first you need to share location from remote system then it's possible.
try{
String strLine="";
NtlmPasswordAuthentication auth = new NtlmPasswordAuthentication("WORKGROUP", "username", "passwd"); // Authentication info here, domain can be null
// try (InputStream is = new SmbFile("smb://DESKTOP-0xxxx/usr/local/cache/abc.txt", auth).getInputStream()) {
try (InputStream is = new SmbFile("smb://xx.xx.xx.xxx/dina_share/abc.txt", auth).getInputStream()) {
BufferedReader br = new BufferedReader(new InputStreamReader(is));
while ((strLine = br.readLine()) != null) {
System.out.println(strLine);
}
} catch (IOException e) {
e.printStackTrace();
}
String smbURL="smb://xx.xx.xx.xxx/dina_share/abcOther.txt";
SmbFileOutputStream fos = new SmbFileOutputStream(new SmbFile(smbURL,auth));
byte bytes[]="Wellcome to you".getBytes();
fos.write(bytes);
}catch(Exception e){
e.printStackTrace();
}