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How to piece together String using file reader and char array

Wrote a file in another class and now I'm trying to piece together the file into a JLabel, so I need to convert the name in the file into a string. Using FileReader and a char array to separate each character into an array to be put together in the JLabel.
I'm getting this error on NamePieces[x] = (char)nr;:
Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0
at clients.initialize(clients.java:197)
at clients.<init>(clients.java:72)
This is the code that I want to read the file:
try(FileReader nameReader = new FileReader(NamePath)) {
int nr = nameReader.read();
int x = 0;
while(nr != -1) {
namePieces[x] = (char)nr;
nr = nameReader.read();
x++;
}
}
catch (FileNotFoundException e) {}
catch (IOException e1) {}
String name = String.valueOf(namePieces[0]) + namePieces[1];
Doesn't work

Most likely, your problem occurs because namePieces is not initialized. As was already mentioned in the comments, you should not use char[] as a container for your characters (because in real world you won't know the length of the files' contents every time, so you will probably need to resize your container), it is way more better to use StringBuilder, provided by Java standard library. It will protect you from getting out of bounds.
StringBuilder namePieces = new StringBuilder();
File file = new File(filePath);
BufferedReader reader = new BufferedReader(
new InputStreamReader(new FileInputStream(file),
Charset.forName("UTF-8")));
int c;
while((c = reader.read()) != -1) {
namePieces.append((char) c);
}
String nameString = namePieces.toString(); // Use this string as a complete array of needed characters
As you see I changed an approach by using not only StringBuilder, but also BufferedReader. However, for your task you can leave FileReader as it is. Just consider appending characters to builder.

If your file just contains a String there is a straightforward way to read it:
public String readMyFile( String fileName) throws IOException {
Path path = Paths.get(fileName);
return Files.readAllLines(path).get(0);
}

Read from file with BufferedReader

Basically I've got an assignment which reads multiple lines from a .txt file.
There are 4 values in the text file per line and each value is separated by 2 spaces.
There are about 10 lines of data in the file.
After taking the input from the file the program then puts it onto a Database. The database connection functionality works fine.
My issue now is with reading from the file using a BufferedReader.
The issue is that if I uncomment any 1 of the 3 lines at the bottom the BufferedReader reads every other line. And if I don't use them then there's an exception as the next input is of type String.
I have contemplated using a Scanner with the .hasNextLine() method.
Any thoughts on what could be the problem and how to fix it?
Thanks.
File file = new File(FILE_INPUT_NAME);
FileReader fr = new FileReader(file);
BufferedReader readFile = new BufferedReader(fr);
String line = null;
while ((line = readFile.readLine()) != null) {
String[] split = line.split(" ", 4);
String id = split[0];
nameFromFile = split[1];
String year = split[2];
String mark = split[3];
idFromFile = Integer.parseInt(id);
yearOfStudyFromFile = Integer.parseInt(year);
markFromFile = Integer.parseInt(mark);
//line = readFile.readLine();
//readFile.readLine();
//System.out.println(readFile.readLine());
}
Edit: There was an error in the formatting of the .txt file. a missing value.
But now I get an ArrayOutOfBoundsException.
Edit edit: Another error in the .txt file! Turns out there was a single space instead of a double. It seems to be working now. But any advice on how to deal with file errors like this in the future?

The issue is that if I uncomment any 1 of the 3 lines at the bottom the BufferedReader reads every other line.
Correct. If you put any of those lines of code in, the line of text read will be thrown away and not processed. You're already reading in the while condition. You don't need another read. If you put any of those lines in, they will be thrown away and not proce

A compilable version of the code posted could be
public void read() throws IOException {
File file = new File(FILE_INPUT_NAME);
FileReader fr = new FileReader(file);
BufferedReader readFile = new BufferedReader(fr);
String line;
while ((line = readFile.readLine()) != null) {
String[] split = line.split(" ", 4);
if (split.length != 4) { // Not enough tokens (e.g., empty line) read
continue;
}
String id = split[0];
String nameFromFile = split[1];
String year = split[2];
String mark = split[3];
int idFromFile = Integer.parseInt(id);
int yearOfStudyFromFile = Integer.parseInt(year);
int markFromFile = Integer.parseInt(mark);
//line = readFile.readLine();
//readFile.readLine();
//System.out.println(readFile.readLine());
}
}
The above uses a single space (" " instead of the original " "). To split on any number of changes, a regular expression can be used, e.g. "\\s+". Of course, exactly 2 spaces can also be used, if that reflects the structure of the input data.
What the method should do with the extracted values (e.g., returning them in an object of some type, or saving them to a database directly), is up to the application using it.

How to remove first line of a text file in java [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Replace first line of a text file in Java
Java - Find a line in a file and remove
I am trying to find a way to remove the first line of text in a text file using java. Would like to use a scanner to do it...is there a good way to do it without the need of a tmp file?
Thanks.

If your file is huge, you can use the following method that is performing the remove, in place, without using a temp file or loading all the content into memory.
public static void removeFirstLine(String fileName) throws IOException {
RandomAccessFile raf = new RandomAccessFile(fileName, "rw");
//Initial write position
long writePosition = raf.getFilePointer();
raf.readLine();
// Shift the next lines upwards.
long readPosition = raf.getFilePointer();
byte[] buff = new byte[1024];
int n;
while (-1 != (n = raf.read(buff))) {
raf.seek(writePosition);
raf.write(buff, 0, n);
readPosition += n;
writePosition += n;
raf.seek(readPosition);
}
raf.setLength(writePosition);
raf.close();
}
Note that if your program is terminated while in the middle of the above loop you can end up with duplicated lines or corrupted file.

Scanner fileScanner = new Scanner(myFile);
fileScanner.nextLine();
This will return the first line of text from the file and discard it because you don't store it anywhere.
To overwrite your existing file:
FileWriter fileStream = new FileWriter("my/path/for/file.txt");
BufferedWriter out = new BufferedWriter(fileStream);
while(fileScanner.hasNextLine()) {
String next = fileScanner.nextLine();
if(next.equals("\n"))
out.newLine();
else
out.write(next);
out.newLine();
}
out.close();
Note that you will have to be catching and handling some IOExceptions this way. Also, the if()... else()... statement is necessary in the while() loop to keep any line breaks present in your text file.

Without temp file you must keep everything in main memory. The rest is straight forward: loop over the lines (ignoring the first) and store them in a collection. Then write the lines back to disk:
File path = new File("/path/to/file.txt");
Scanner scanner = new Scanner(path);
ArrayList<String> coll = new ArrayList<String>();
scanner.nextLine();
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
coll.add(line);
}
scanner.close();
FileWriter writer = new FileWriter(path);
for (String line : coll) {
writer.write(line);
}
writer.close();

If file is not too big, you can read is into a byte array, find first new line symbol and write the rest of array into the file starting from position zero. Or you may use memory mapped file to do so.

Capture data read from file into string stream Java

I'm coming from a C++ background, so be kind on my n00bish queries...
I'd like to read data from an input file and store it in a stringstream. I can accomplish this in an easy way in C++ using stringstreams. I'm a bit lost trying to do the same in Java.
Following is a crude code/way I've developed where I'm storing the data read line-by-line in a string array. I need to use a string stream to capture my data into (rather than use a string array).. Any help?
char dataCharArray[] = new char[2];
int marker=0;
String inputLine;
String temp_to_write_data[] = new String[100];
// Now, read from output_x into stringstream
FileInputStream fstream = new FileInputStream("output_" + dataCharArray[0]);
// Convert our input stream to a BufferedReader
BufferedReader in = new BufferedReader (new InputStreamReader(fstream));
// Continue to read lines while there are still some left to read
while ((inputLine = in.readLine()) != null )
{
// Print file line to screen
// System.out.println (inputLine);
temp_to_write_data[marker] = inputLine;
marker++;
}
EDIT:
I think what I really wanted was a StringBuffer.
I need to read data from a file (into a StringBuffer, probably) and write/transfer all the data back to another file.

In Java, first preference should always be given to buying code from the library houses:
http://commons.apache.org/io/api-1.4/org/apache/commons/io/IOUtils.html
http://commons.apache.org/io/api-1.4/org/apache/commons/io/FileUtils.html
In short, what you need is this:
FileUtils.readFileToString(File file)

StringBuffer is one answer, but if you're just writing it to another file, then you can just open an OutputStream and write it directly out to the other file. Holding a whole file in memory is probably not a good idea.

In you simply want to read a file and write another one:
BufferedInputStream in = new BufferedInputStream( new FileInputStream( "in.txt" ) );
BufferedOutputStream out = new BufferedOutputStream( new FileOutputStream( "out.txt" ) );
int b;
while ( (b = in.read()) != -1 ) {
out.write( b );
}
If you want to read a file into a string:
StringWriter out = new StringWriter();
BufferedReader in = new BufferedReader( new FileReader( "in.txt" ) );
int c;
while ( (c = in.read()) != -1 ) {
out.write( c );
}
StringBuffer buf = out.getBuffer();
This can be made more efficient if you read using byte arrays. But I recommend that you use the excellent apache common-io. IOUtils (http://commons.apache.org/io/api-1.4/org/apache/commons/io/IOUtils.html) will do the loop for you.
Also, you should remember to close the streams.

I also come from C++, and I was looking for a class similar to the C++ 'StringStreamReader', but I couldn't find it. In my case (which I think was very simple), I was trying to read a file line by line and then read a String and an Integer from each of these lines. My final solution was to use two objects of the class java.util.Scanner, so that I could use one of them to read the lines of the file directly to a String and use the second one to re-read the content of each line (now in the String) to the variables (a new String and a positive 'int'). Here's my code:
try {
//"path" is a String containing the path of the file we want to read
Scanner sc = new Scanner(new BufferedReader(new FileReader(new File(path))));
while (sc.hasNextLine()) { //while the file isn't over
Scanner scLine = new Scanner(sc.nextLine());
//sc.nextLine() returns the next line of the file into a String
//scLine will now proceed to scan (i.e. analyze) the content of the string
//and identify the string and the positive 'int' (what in C++ would be an 'unsigned int')
String s = scLine.next(); //this returns the string wanted
int x;
if (!scLine.hasNextInt() || (x = scLine.nextInt()) < 0) return false;
//scLine.hasNextInt() analyzes if the following pattern can be interpreted as an int
//scLine.nextInt() reads the int, and then we check if it is positive or not
//AT THIS POINT, WE ALREADY HAVE THE VARIABLES WANTED AND WE CAN DO
//WHATEVER WE WANT WITH THEM
//in my case, I put them into a HashMap called 'hm'
hm.put(s, x);
}
sc.close();
//we finally close the scanner to point out that we won't need it again 'till the next time
} catch (Exception e) {
return false;
}
return true;
Hope that helped.

Java: Reading the Trailing New Line from a Text File

How can you get the contents of a text file while preserving whether or not it has a newline at the end of the file? Using this technique, it is impossible to tell if the file ends in a newline:
BufferedReader reader = new BufferedReader(new FileReader(fromFile));
StringBuilder contents = new StringBuilder();
String line = null;
while ((line=reader.readLine()) != null) {
contents.append(line);
contents.append("\n");
}

Don't use readLine(); transfer the contents one character at a time using the read() method. If you use it on a BufferedReader, this will have the same performance, although unlike your code above it will not "normalize" Windows-style CR/LF line breaks.

You can read the whole file content using one of the techniques listed here
My favorite is this one:
public static long copyLarge(InputStream input, OutputStream output)
throws IOException {
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
long count = 0;
int n = 0;
while ((n = input.read(buffer))>=0) {
output.write(buffer, 0, n);
count += n;
}
return count;
}