My goal is to read a simple text file, and output it's results.
For some reason, I get an error for not being able to find the file specified, even though it's in the same folder. I'm a little stumped as to why it's not working.
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
class Test
{
public static void main(String[] args)
throws IOException
{
int number;
File inputFile = new File("input.txt");
Scanner file = new Scanner(inputFile);
while(file.hasNext()) {
number = file.nextInt();
System.out.println(number);
}
System.out.println("End of file detected");
}
}
That file needs to be immediate inside your project folder. If its still not working you can use absolute path instead of relative path as alternative.
like e.g D:\\test.txt
Which folder are you talking about? If you are executing the app from Eclipse, the textfile must be in the directory where .project, .classpath, etc. files and folders are.
Here is a way to choose a file graphically using JOptionPane
ArrayList<String> lines = new ArrayList<>();
JOptionPane.showMessageDialog(null, "Please choose a file");
JFileChooser input = new JFileChooser();
int a = input.showOpenDialog(null);
String file = "";
if (a == JFileChooser.APPROVE_OPTION) {
File selectedFile = input.getSelectedFile();
file = selectedFile.getPath();
}
//use file input to read in line one at a time
FileInputStream fstream = new FileInputStream(file);
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = br.readLine()) != null) {
lines.add(line);
}
Related
Let's say I have a txt file that has the whole dictionary in it. how would I make this code be able to transer only 5-letter words into a new created txt file?
import java.io.*;
public class wordwebster {
public static void main(String[] args) throws IOException {
int five = 0;
File directory = new File(".");
String webster = directory.getCanonicalPath() + File.separator+ "webster.txt";
String fiveLetterWords = directory.getCanonicalPath()+ File.separator +"fiveLetterWords.txt";
File fin = new File(webster);
FileInputStream file = new FileInputStream(fin);
BufferedReader input = new BufferedReader(new InputStreamReader(file));
FileWriter fileStream = new FileWriter(fiveLetterWords,true);
BufferedWriter output = new BufferedWriter(fileStream);
String line = null;
while ((line = input.readLine())!= null){
output.write(line);
output.newLine();
}
input.close();
output.close();
}
}
EDIT:
As asked, let's say the input file (webster.txt) contain the words
Sentence
Frequent
Hello
Send
Variety
False
I would need only five letter words be extracted (Hello and False) and be put into a new file (fiveLetterWords.txt).
If you need to allow only words whose length is exactly five, you can just put an if condition to check before writing into file. Modify your while loop to this,
while ((line = input.readLine()) != null) {
if (line.trim().length() == 5) {
output.write(line);
output.newLine();
}
}
Hope this helps. Let me know if you face any issues.
How does one use a specified file path rather than a file from the resource folder as an input or output stream? This is the class I have and I would like to read from a specific file path instead of placing the txt file in the resources folder in IntelliJ. Same for an output stream. Any help rendered would be appreciated thanks.
Input Stream
import java.io.*;
import java.util.*;
public class Example02 {
public static void main(String[] args) throws FileNotFoundException {
// STEP 1: obtain an input stream to the data
// obtain a reference to resource compiled into the project
InputStream is = Example02.class.getResourceAsStream("/file.txt");
// convert to useful form
Scanner in = new Scanner(is);
// STEP 2: do something with the data stream
// read contents
while (in.hasNext()) {
String line = in.nextLine();
System.out.println(line);
}
// STEP 3: be polite, close the stream when done!
// close file
in.close();
}
}
Output stream
import java.io.*;
public class Example03
{
public static void main(String []args) throws FileNotFoundException
{
// create/attach to file to write too
// using the relative filename will cause it to create the file in
// the PROJECT root
File outFile = new File("info.txt");
// convert to a more useful writer
PrintWriter out = new PrintWriter(outFile);
//write data to file
for(int i=1; i<=10; i++)
out.println("" + i + " x 5 = " + i*5);
//close file - required!
out.close();
}
}
Preferred way for getting InputStream is java.nio.file.Files.newInputStream(Path)
try(final InputStream is = Files.newInputStream(Paths.get("/path/to/file")) {
//Do something with is
}
Same for OutputStream Files.newOutputStream()
try(final OutputStream os = Files.newOutputStream(Paths.get("/path/to/file")) {
//Do something with os
}
Generally, here is official tutorial from Oracle to working with IO.
First you have to define the path you want to read the file from, absolute path like so:
String absolutePath = "C:/your-dir/yourfile.txt"
InputStream is = new FileInputStream(absolutePath);
It's similar for writing the file as well:
String absolutePath = "C:/your-dir/yourfile.txt"
PrintWriter out = new PrintWriter(new FileOutputStream(absolutePath));
You can use a file object as:
File input = new File("C:\\[Path to file]\\file.txt");
So i am working on a code that receives 2 strings. The string are "input#.txt" or "output#.txt" the # symbol is replaced with whatever number file is used. Now in the input file is the information I need to get to. How do I determine if that input.txt file can be opened and how do I open it.
I've tried a buffered reader and trying to just make the string a file.
import java.util.*;
import java.io.*;
public class Robot {
public static void readInstructions(String inputFileName, String outputFileName) throws InvalidRobotInstructionException{
try{
BufferedReader input = new BufferedReader(new FileReader(inputFileName));
File inner = new File(inputFileName);
Scanner in = new Scanner(input);
PrintWriter wrt;
wrt = new PrintWriter(outputFileName);
if(input.readLine() == null){
System.out.println("Input file not found.");
return;
}
This will read a file in:
Scanner input = new Scanner(new File("input5.txt"));
Don't forget to add throws FileNotFoundException in your main method
edit: I see you added code.
I have file in my computer which have .file extension , I want to read it 9 character by 9 character. I know that I can read file by this code, but what should I do when my file is not .txt?does java support to read .file s with this code?
InputStream is = null;
InputStreamReader isr = null;
BufferedReader br = null;
is = new FileInputStream("c:/test.txt");
// create new input stream reader
isr = new InputStreamReader(is);
// create new buffered reader
br = new BufferedReader(isr);
// creates buffer
char[] cbuf = new char[is.available()];
for (int i = 0; i < 90000000; i += 9) {
// reads characters to buffer, offset i, len 9
br.read(cbuf, i, 9);}
The extension of a file is totally irrelevant. Extensions like .txt are mere conventions to help your operating system choose the right program when you open it.
So you can store text in any file (.txt, .file, .foobar if you are so inclined...), provided you know what kind of data it contains, and read it accordingly from your program.
So yes, Java can read .file files, and your code will work fine if that file contains text.
does java support to read .file s with this code?
No, since c:/test.txt is hard coded. If it wouldn't yes it would support it.
Yes it's possible if you write is = new FileInputStream("c:/test.file");
Yes, it reads any file you give it the same way. You can pass any file path with any extension to the FileInputStream constructor.
Anyone can read any file you want, since a file is just a sequence of bytes. The extension tells you in what format the bytes should be read, so when we have a .txt file we know that this is a file with sequences of characters.
When you have a file format called .file we know that it should be (according to you) a 9x9 set of characters. This way we know what to read and do that.
Since the .file format is characters I would say yes, you can read that with your code for instance with this:
public String[] readFileFormat (final File file) throws IOException {
if (file.exists()) {
final String[] lines = new String[9];
final BufferedReader reader = new BufferedReader ( new FileReader( file ) );
for ( int i = 0; i < lines.length; i++ ) {
lines[i] = reader.readLine();
if (lines[i] == null || lines[i].isEmpty() || lines[i].length() < 9)
throw new RuntimeException ("Line is empty when it should be filled!");
else if (lines[i].length() > 9)
throw new RuntimeException ("Line does not have exactly 9 characters!");
}
reader.close();
return lines;
}
return null;
}
The extension is totally irrelevant, so it can be .file, .txt or whatever you want it to be.
Here is an example of reading in a file with BuffereInputStream that reads a file of type .file. This is part of a larger guide that discusses 15 ways to read files in Java.
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class ReadFile_BufferedInputStream_Read {
public static void main(String [] pArgs) throws FileNotFoundException, IOException {
String fileName = "c:\\temp\\sample-10KB.file";
File file = new File(fileName);
FileInputStream fileInputStream = new FileInputStream(file);
try (BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream)) {
int singleCharInt;
char singleChar;
while((singleCharInt = bufferedInputStream.read()) != -1) {
singleChar = (char) singleCharInt;
System.out.print(singleChar);
}
}
}
}
I have a slight problem trying to save a file in java.
For some reason the content I get after saving my file is different from what I have when I read it.
I guess this is related to file encoding, but without being sure.
Here is test code I put together. The idea is basically to read a file, and save it again.
When I open both files, they are different.
package workspaceFun;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import org.apache.commons.codec.DecoderException;
public class FileSaveTest {
public static void main(String[] args) throws IOException, DecoderException{
String location = "test.location";
File locationFile = new File(location);
FileInputStream fis = new FileInputStream(locationFile);
InputStreamReader r = new InputStreamReader(fis, Charset.forName("UTF-8"));
System.out.println(r.getEncoding());
StringBuilder builder = new StringBuilder();
int ch;
while((ch = fis.read()) != -1){
builder.append((char)ch);
}
String fullLocationString = builder.toString();
//Now we want to save back
FileOutputStream fos = new FileOutputStream("C:/Users/me/Desktop/test");
byte[] b = fullLocationString.getBytes();
fos.write(b);
fos.close();
r.close();
}
}
An extract from the input file (opened as plain text using Sublime 2):
40b1 8b81 23bc 0014 1a25 96e7 a393 be1e
and from the output file :
40c2 b1c2 8bc2 8123 c2bc 0014 1a25 c296
The getEncoding method returns "UTF8". Trying to save the output file using the same charset doest not seem to solve the issue.
What puzzles me is that when I try to read the input file using Hex from apache.commons.codec like this :
String hexLocationString2 = Hex.encodeHexString(fullLocationString.getBytes("UTF-8"));
The String already looks like my output file, not the input.
Would you have any idea on what can go wrong?
Thanks
Extra info for those being interested, I am trying to read an eclipse .location file.
EDIT: I placed the file online so that you can test the code
I believe is the way you are reading the stream.
You are using FileInputStream directly to read the content instead of wrapping it in the InputStreamReader
By using the InputStreamReader you may determine which Charset to use.
Take in consideration that the Charset defined in the InputStream must be the same you expect as InputStream doesn't detect charsets, it just reads them in that specific format.
Try the following changes:
InputStreamReader r = new InputStreamReader(new FileInputStream(locationFile), StandardCharsets.UTF_8);
then instead of fos.read() use r.read()
Finally when writing the String get the bytes in the same Charset as your Reader
FileOutputStream fos = new FileOutputStream("C:/Users/me/Desktop/test");
fos.write(fullLocationString.getBytes(StandardCharsets.UTF_8));
fos.close()
Try to read and write back as below:
public class FileSaveTest {
public static void main(String[] args) throws IOException {
String location = "D:\\test.txt";
BufferedReader br = new BufferedReader(new FileReader(location));
StringBuilder sb = new StringBuilder();
try {
String line = br.readLine();
while (line != null) {
sb.append(line);
line = br.readLine();
if (line != null)
sb.append(System.lineSeparator());
}
} finally {
br.close();
}
FileOutputStream fos = new FileOutputStream("D:\\text_created.txt");
byte[] b = sb.toString().getBytes();
fos.write(b);
fos.close();
}
}
Test file contains both Cirillic and Latin characters.
SDFASDF
XXFsd1
12312
іва