I am create a new file
File f = new File(file_path);
then the end of program can i possible to close that the file object or file?
f.close();
else there is a method is possible to close file??
public class etest2read {
public static void main(String[] args) throws IOException {
File dir = new File("input");
String source = dir.getCanonicalPath() + File.separator + "TestFile.txt";
//String TestFileone = dir.getCanonicalPath() + File.separator + "TestFileone.txt";
File fin = new File(source);
FileInputStream fis = new FileInputStream(fin);
BufferedReader br = new BufferedReader(new InputStreamReader(fis));
System.out.println("file/folder: "+fin.getAbsolutePath());
System.out.println("file/folder: "+dir.getCanonicalPath());
System.out.println("file/folder: "+fin.lastModified());
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println (strLine);
}
//Close the input stream
br.close();
System.out.println("Closed Buffered Reader");
fis.close();
System.out.println("Closed File Input Stream");
fin.close(); // providing the error
}
}
No it is not possible.
A File is an abstract representation of a file or directory pathname. You do not open the File, only a Stream or a Reader on that File.
No. You can only close the instances of objects that implement the Closeable interface (example Reader , InputStream etc). File class doesn't implement Closeable. Like Burkahard says, it is merely an abstract representation of the underlying file/ directory
Related
I have tried to implement a simple program to delete a particular text from a file, some how it is not able to delete it. I am reading entire file content into a temp file , delete the user input string from it and update the content to the original file.
Any help would be highly appreciated.
public class TextEraser{
public static void main(String[] args) throws IOException {
System.out.print("Enter a string to remove : ");
Scanner scanner = new Scanner(System. in);
String inputString = scanner. nextLine();
// Locate the file
File file = new File("/Users/lobsang/documents/input.txt");
//create temporary file
File temp = File.createTempFile("file", ".txt", file.getParentFile());
String charset = "UTF-8";
try {
// Create a buffered reader
// to read each line from a file.
BufferedReader in = new BufferedReader(new FileReader(file));
PrintWriter writer = new PrintWriter(new OutputStreamWriter(new FileOutputStream(temp), charset));
String s = in.readLine();
// Read each line from the file and echo it to the screen.
while (s !=null) {
s=s.replace(inputString,"");
s = in.readLine();
}
writer.println(s);
// Close the buffered reader
in.close();
writer.close();
file.delete();
temp.renameTo(file);
} catch (FileNotFoundException e1) {
// If this file does not exist
System.err.println("File not found: " + file);
}
}
After replace with input string, write string immediate in file.
while (s != null) {
s = s.replace(inputString, "");
writer.write(s);
// writer.newLine();
s = in.readLine();
}
For new line , use BufferedWriter in place of PrintWriter, it contains method newLine()
writer.newLine();
Remove this
writer.println(s);
I tried it this way but it doesn't find the textfile.
try {
FileInputStream fstream = new FileInputStream("textfile.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
// Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println(strLine);
}
// Close the input stream
in.close();
} catch (Exception e) {// Catch exception if any
System.err.println("Error: " + e.getMessage());
}
All files are in the same package.
Your text file is inside a the package "trainer" which is inside "src" so when you request it, you must use "src/trainer/textfile.txt". The preceding / denotes the root of the application and is optional if you're not exporting to runnable jars for example.
FileInputStream fstream = new FileInputStream("src/trainer/textfile.txt");
I am getting this error in my code when trying to read a file saved on the external storage of my phone :
java.io.FileNotFoundException: shopping.txt: open failed: ENOENT (No such file or directory)
I can manage to write data to this file with success, what I did a lot of times.
However, I cannot access for reading this same file, giving the entire path or through another method.
The code writing and saving successfully :
File path = new File(this.getFilesDir().getPath());
String value = "vegetables";
// File output = new File(path + File.separator + fileName);
File output = new File(getApplicationContext().getExternalFilesDir(null),"shopping.txt");
try {
FileOutputStream fileout = new FileOutputStream(output.getAbsolutePath());
OutputStreamWriter outputWriter=new OutputStreamWriter(fileout);
outputWriter.write(value);
outputWriter.close();
//display file saved message
// Toast.makeText(getBaseContext(), "File saved successfully!",
// Toast.LENGTH_LONG).show();
Toast.makeText(MainActivity.this,String.valueOf(output),Toast.LENGTH_LONG).show();
Log.d("MainActivity", "Chemin fichier = [" + output + "]");
}
catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
The writing piece of code crashing my app :
try
{
File gFile;
FileInputStream fis = new FileInputStream (new File("shopping.txt"));
//FileInputStream fis = openFileInput("/storage/emulated/0/Android/data/com.example.namour.shoppinglist/files/shopping.txt");
BufferedReader reader = new BufferedReader(new InputStreamReader(fis));
String line = null, input="";
while ((line = reader.readLine()) != null)
input += line;
Toast.makeText(MainActivity.this,line,Toast.LENGTH_LONG).show();
reader.close();
fis.close();
Toast.makeText(MainActivity.this,"Read successful",Toast.LENGTH_LONG).show();
//return input;
}
catch (IOException e)
{
Log.e("Exception", "File read failed: " + e.toString());
//toast("Error loading file: " + ex.getLocalizedMessage());
}
What am I doing wrong ?
For sure, not a problem of permissions, since I can write with success.
Many thanks for your help.
You missed to specifiy the correct path. You are looking for a file named shopping.txt in your current working directory (at runtime).
Create a new File object with the correct path and it will work:
File input = new File(getApplicationContext().getExternalFilesDir(null),"shopping.txt");. You could reuse your object from writing.
While opening the file, you are simply using new File("shopping.txt").
You need to specify the parent folder, like this:
new File(getExternalFilesDir(),"shopping.txt");
I recommend you make sure of org.apache.commons.io for IO, their FileUtils and FileNameUtils libs are great. ie: FileUtils.writeStringToFile(new File(path), data); Add this to gradle if you wish to use it: implementation 'org.apache.commons:commons-collections4:4.1'
In regards to your problem. When you write your file you are using:
getApplicationContext().getExternalFilesDir(null),"shopping.txt"
But when reading your file you are using:
FileInputStream fis = new FileInputStream (new File("shopping.txt"));
Notice that you didn't specify a path to shopping.txt simply the file name.
Why not do something like this instead:
//Get path to directory of your choice
public String GetStorageDirectoryPath()
{
String envPath = Environment.getExternalStorageDirectory().toString();
String path = FilenameUtils.concat(envPath, "WhateverDirYouWish");
return path;
}
//Concat filename with path
public String GetFilenameFullPath(String fileName){
return FilenameUtils.concat(GetStorageDirectoryPath(), fileName);
}
//Write
String fullFilePath = GetFilenameFullPath("shopping.txt");
FileUtils.writeStringToFile(new File(fullFilePath ), data);
//Read
File file = new File(fullFilePath);
StringBuilder text = new StringBuilder();
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null){
text.append(line);
if(newLine)
text.append(System.getProperty("line.separator"));
}
br.close();
So I wrote this file reader method that should return a string of everything that is in the file, but it isn't working properly. Writing into the file works perfectly, but this reading method doesn't. What the method does currently is it reads the last string/text added, but it does not read the file from start to finish. 'br' is my bufferedReader, which is declared somewhere else in the same class.
Here's how br is defined:
private static FileInputStream fis;
private static BufferedReader br;
and then in the constructor:
fis = new FileInputStream(file);
br = new BufferedReader(new InputStreamReader(fis));
Here's the method:
public String readStuff(){
String line = "";
String r = "";
try{
while((line = br.readLine()) != null){
System.out.println(line + " read ");
r+= line;
}
//br.close(); JDK 7 does this automatically apparently
}catch(IOException e){
e.printStackTrace();
System.out.println("Error at readStuff!");
}
return r;
I know I'm making either a logic mistake or some obvious error, I just don't know where.
If you want to read the entire file twice, you will have to close it and open new streams/readers next time.
Those streams/readers should be local to the method, not members, and certainly not static.
Using File and FileReader You can Read / Write File From Dir.
you can get File using File class object
File file = new File("file.txt");
and After Process to read that file
FileReader fr = new FileReader(file);
There are Whole Code to read File...
File file = new File("G:\\Neon\\data.txt");
FileReader fr = new FileReader(file);
String data = "";
while((i = fr.read()) != -1)
{
data = data + (char)i;
}
System.out.println(data);
How do you read and display data from .txt files?
BufferedReader in = new BufferedReader(new FileReader("<Filename>"));
Then, you can use in.readLine(); to read a single line at a time. To read until the end, write a while loop as such:
String line;
while((line = in.readLine()) != null)
{
System.out.println(line);
}
in.close();
If your file is strictly text, I prefer to use the java.util.Scanner class.
You can create a Scanner out of a file by:
Scanner fileIn = new Scanner(new File(thePathToYourFile));
Then, you can read text from the file using the methods:
fileIn.nextLine(); // Reads one line from the file
fileIn.next(); // Reads one word from the file
And, you can check if there is any more text left with:
fileIn.hasNext(); // Returns true if there is another word in the file
fileIn.hasNextLine(); // Returns true if there is another line to read from the file
Once you have read the text, and saved it into a String, you can print the string to the command line with:
System.out.print(aString);
System.out.println(aString);
The posted link contains the full specification for the Scanner class. It will be helpful to assist you with what ever else you may want to do.
In general:
Create a FileInputStream for the file.
Create an InputStreamReader wrapping the input stream, specifying the correct encoding
Optionally create a BufferedReader around the InputStreamReader, which makes it simpler to read a line at a time.
Read until there's no more data (e.g. readLine returns null)
Display data as you go or buffer it up for later.
If you need more help than that, please be more specific in your question.
I love this piece of code, use it to load a file into one String:
File file = new File("/my/location");
String contents = new Scanner(file).useDelimiter("\\Z").next();
Below is the code that you may try to read a file and display in java using scanner class. Code will read the file name from user and print the data(Notepad VIM files).
import java.io.*;
import java.util.Scanner;
import java.io.*;
public class TestRead
{
public static void main(String[] input)
{
String fname;
Scanner scan = new Scanner(System.in);
/* enter filename with extension to open and read its content */
System.out.print("Enter File Name to Open (with extension like file.txt) : ");
fname = scan.nextLine();
/* this will reference only one line at a time */
String line = null;
try
{
/* FileReader reads text files in the default encoding */
FileReader fileReader = new FileReader(fname);
/* always wrap the FileReader in BufferedReader */
BufferedReader bufferedReader = new BufferedReader(fileReader);
while((line = bufferedReader.readLine()) != null)
{
System.out.println(line);
}
/* always close the file after use */
bufferedReader.close();
}
catch(IOException ex)
{
System.out.println("Error reading file named '" + fname + "'");
}
}
}
If you want to take some shortcuts you can use Apache Commons IO:
import org.apache.commons.io.FileUtils;
String data = FileUtils.readFileToString(new File("..."), "UTF-8");
System.out.println(data);
:-)
public class PassdataintoFile {
public static void main(String[] args) throws IOException {
try {
PrintWriter pw = new PrintWriter("C:/new/hello.txt", "UTF-8");
PrintWriter pw1 = new PrintWriter("C:/new/hello.txt");
pw1.println("Hi chinni");
pw1.print("your succesfully entered text into file");
pw1.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
BufferedReader br = new BufferedReader(new FileReader("C:/new/hello.txt"));
String line;
while((line = br.readLine())!= null)
{
System.out.println(line);
}
br.close();
}
}
In Java 8, you can read a whole file, simply with:
public String read(String file) throws IOException {
return new String(Files.readAllBytes(Paths.get(file)));
}
or if its a Resource:
public String read(String file) throws IOException {
URL url = Resources.getResource(file);
return Resources.toString(url, Charsets.UTF_8);
}
You most likely will want to use the FileInputStream class:
int character;
StringBuffer buffer = new StringBuffer("");
FileInputStream inputStream = new FileInputStream(new File("/home/jessy/file.txt"));
while( (character = inputStream.read()) != -1)
buffer.append((char) character);
inputStream.close();
System.out.println(buffer);
You will also want to catch some of the exceptions thrown by the read() method and FileInputStream constructor, but those are implementation details specific to your project.