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BufferedReader is closed when returned from method

I'm writing code to read a file and process it and I'm splitting logic into many small methods. So I have a method to read the file and return BufferedReader and another one to do logic with the returned BufferedReader object. But when I try to read lines from the BufferedReader object in the second method it gives me [java.io.IOException: Stream Closed].
The method I used to read the file and return BufferedReader
private static BufferedReader readFile(String file) {
try (FileInputStream fileInputStream = new FileInputStream(file)) {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(fileInputStream));
System.out.println(bufferedReader.readLine()); // this line is working successfully
return bufferedReader;
} catch (FileNotFoundException fileNotFoundException) {
fileNotFoundException.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
Any idea why the happens and how to solve it ?

You are using try-with-resources:
try (FileInputStream fileInputStream = new FileInputStream(file)) {
This line is creating a FileInputStream which can be used inside your try block. As soon as you leave your try block, the close() method will be called onto the stream. So if you return the stream or its BufferedReader, the stream will already be closed. You should not use try-with-resources or even better, return whatever you need from the stream instead of the stream itself.

Obviously, the problem here lies in the use of try-with-resources, and AutoCloseable interface. However, i would like to point out that the way you read the file is the "old fashioned" way. We now have the Files, Paths, and Stream classes to facilitate reading of files. this uses java NIO, returns a Stream and is better overall:
Files.lines(Paths.get(pathToFile))
additionally, nothing has to be closed here

Does nested resource acquisition require special handling in Java?

First of all, yes, try-with-resource fixes any of these questions... but I can't see how this exactly works without it.
Let's look at this code from the java documentation as an example, which can be found here:
static String readFirstLineFromFileWithFinallyBlock(String path)
throws IOException {
BufferedReader br = new BufferedReader(new FileReader(path));
try {
return br.readLine();
} finally {
if (br != null) br.close();
}
}
Now, the resource is released on br.close() if it was acquired. However,
What happens if new FileReader(path) succeeds and then new BufferedReader(...) throws an exception?
How does java guarantee that the FileReader is closed?
Is it guaranteed that creating a BufferedReader on an already opened FileReader will always succeed? If so, why is that method declared as throwing an IOException?
Or should we instead be writing the following to make sure that situation doesn't happen?
static String readFirstLineFromFileWithFinallyBlock(String path)
throws IOException {
FileReader fr;
try {
FileReader fr = new FileReader(path);
BufferedReader br;
try {
BufferedReader br = new BufferedReader(fr);
return br.readLine();
} finally {
if (br != null) br.close();
}
finally {
// Implements closeable, so it is ok if we call it twice.
if (fr != null) fr.close();
}
}
Of course, using try-with-resources, this nested mess disappears nonetheless, since we can declare multiple resources in the same statement. But I always see myself writing try-with-resources as a way to avoid thinking at all about exactly this situation, and trying to find a solution online I really couldn't.
Any help would be appreciated, thanks!

The tutorials are often out of date or don't describe good practice.
If we look at the first piece of code you quoted, br can never be null. The if ( ) can be removed. This was probably caused by previous code by previous code mixing to finally with a catch. If a try statement has both finally and a catch it is probably wrong and almost certainly doing something ill advised. Typically you'd see a null dance going on and at least one obvious bug.
The received wisdom on this issue is that BufferedReader will only fail if something has gone horribly wrong with your entire process. Perhaps out of memory or the stack have overflowed. If you get those sorts of exceptions you probably want to bail out of altogether.
The pedantic way of writing the code without try-with-resource is:
FileReader fr = new FileReader(path);
try {
BufferedReader br = new BufferedReader(fr);
return br.readLine();
} finally {
fr.close();
}
However, in some case you may get this wrong. Considered BufferWriter. You've forgotten to flush that, haven't you? I mean, I would. If you closed that in a finally, it wouldn't have been a problem. Also some decorators are resources themselves. For instance, they may have a native implementation that uses non-garbage collected memory. That isn't necessarily documented.
Closing both resource and decorator isn't difficult, but does kind of head towards the right without try with resource.
// (Using same example even though it doesn't matter here - imaging a Writer)
FileReader fr = new FileReader(path);
try {
BufferedReader br = new BufferedReader(fr);
try {
return br.readLine();
} finally {
br.close();
}
} finally {
fr.close();
}

Look in java source code at implementation of close() for BufferedReader.
* #see FileReader
* #see InputStreamReader
* #see java.nio.file.Files#newBufferedReader
*
* #author Mark Reinhold
* #since 1.1
*/
public class BufferedReader extends Reader {
private Reader in;
...
public void close() throws IOException {
synchronized (lock) {
if (in == null)
return;
try {
in.close();
} finally {
in = null;
cb = null;
}
}
}
...
/**
* Creates a buffering character-input stream that uses an input buffer of
* the specified size.
*
* #param in A Reader
* #param sz Input-buffer size
*
* #exception IllegalArgumentException If {#code sz <= 0}
*/
public BufferedReader(Reader in, int sz) {
super(in);
if (sz <= 0)
throw new IllegalArgumentException("Buffer size <= 0");
this.in = in;
cb = new char[sz];
nextChar = nChars = 0;
}
/**
* Creates a buffering character-input stream that uses a default-sized
* input buffer.
*
* #param in A Reader
*/
public BufferedReader(Reader in) {
this(in, defaultCharBufferSize);
}
so close() is taken care of Reader (FileReader here) and set it to null.
Simply BufferedReader br = new BufferedReader(new FileReader(path)) is fine
Does nested resource acquisition require special handling in Java?
here: NO

What happens if new FileReader(path) succeeds and then new BufferedReader(...) throws an exception?
The BufferedReader constructor doesn't throw exceptions. Particularly, it doesn't involve any filesystem operations, so it doesn't throw IOException.
How does java guarantee that the FileReader is closed?
The BufferedReader's close method closes the underlying FileReader.
Is it guaranteed that creating a BufferedReader on an already opened FileReader will always succeed? If so, why is that method declared as throwing an IOException?
You're focusing on the wrong thing. readFirstLineFromFileWithFinallyBlock is marked with throws IOException because every method or constructor invoked besides the BufferedReader constructor can throw IOException. readline, close, and the FileReader constructor can all throw.
If both the FileReader and BufferedReader constructors could fail, and if both objects needed to be closed separately, then you would need two trys.

You can use try with resources instead of releasing resources individually. Please look the below code.
try(BufferedReader bufferedReader = new BufferedReader(new FileReader(""))) {
}catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

BufferedReader is never closed. What are the ramifications?

I'm trying to understand what are the ramifications if the BufferedReader is never closed?
I just realized that many of the static code has a BufferedReader and they are never closed with try...catch..finally (br.close)
most of the code looks like this:
public static boolean isProcessX24Success(String data) throws Exception
{
BufferedReader br = new BufferedReader(new StringReader(data));
String line = "";
String result = "";
while ((line = br.readLine()) != null)
{
if (line.contains("SUCCESS X24"))
return true;
}
return false;
}
As you can see there's no br.close in a finally. Does that present a problem? if so what is it? the call to this method (and other from such nature) is done sequentially --not by multiple threads.

No problems because you use it on a StringReader. When the scope of the BufferedReder is left it will be eligible for garbage collection.
It would be a problem if you did not close e.g a FileReader because the system resource would not be closed properly and there might be a read-lock on the file until the program ends.
When writing it might be a problem, because the data might never be written to the file because of buffering.

Filereader null declarations and appending best practice

I want to optimise my file reader function but am not sure if it is best practice to declare the nulls outside of the try loop. Also, is looping and appending chars to a Stringbuffer considered bad practice? I would like to use the exception handling here, but maybe it is better to use another structure? any advice most welcome, thanks.
public String readFile(){
File f = null;
FileReader fr = null;
StringBuffer content = null;
try{
f = new File("c:/test.txt");
fr = new FileReader(f);
int c;
while((c = fr.read()) != -1){
if(content == null){
content = new StringBuffer();
}
content.append((char)c);
}
fr.close();
}
catch (Exception e) {
throw new RuntimeException("An error occured reading your file");
}
return content.toString();
}
}

Advice:
Indent your code properly. The stuff in your question looks like a dog's breakfast.
You don't need to initialize f inside the try / catch block. The constructor can't throw an Exception the way you are using it.
In fact, you don't need to declare it at all. Just inline the new File(...).
In fact, you don't even need to do that. Use the FileReader(String) constructor.
There's no point initializing the StringBuffer inside the loop. The potential performance benefit is small and only applies in the edge-case where the file is empty or doesn't exist. In all other cases, this is an anti-optimization.
Don't catch Exception. Catch the exceptions that you expect to be thrown and allow all other exceptions to propagate. The unexpected exceptions are going to be due to bugs in your program, and need to be handled differently from others.
When you catch an exception, don't throw away the evidence. For an unexpected exception, either print / log the exception, its message and its stacktrace, or pass it as the 'cause' of the exception that you throw.
The FileReader should be closed in a finally clause. In your version of the code, the FileReader won't be closed if there is an exception after the object has been created and before the close() call. That will result in a leaked file descriptor and could cause problems later in your application.
Better yet, use the new Java 7 "try with resource" syntax which takes care of closing the "resource" automatically (see below).
You are reading from the file one character at a time. This is very inefficient. You need to either wrap the Reader in a BufferedReader, or read a large number of characters at a time using (for example) read(char[], int, int)
Use StringBuilder rather than StringBuffer ... unless you need a thread-safe string assembler.
Wrapping exceptions in RuntimeException is bad practice. It makes it difficult for the caller to handle specific exceptions ... if it needs to ... and even makes printing of a decent diagnostic more difficult. (And that assumes that you didn't throw away the original exception like your code does.)
Note: if you follow the advice of point 8 and not 9, you will find that the initialization of fr to null is necessary if you open the file in the try block.
Here's how I'd write this:
public String readFile() throws IOException {
// Using the Java 7 "try with resource syntax".
try (FileReader fr = new FileReader("c:/test.txt")) {
BufferedReader br = new BufferedReader(fr);
StringBuilder content = new StringBuilder();
int c;
while ((c = br.read()) != -1) {
content.append((char)c);
}
return content.toString();
}
}
A further optimization would be to use File.length() to find out what the file size (in bytes) is and use that as the initial size of the StringBuilder. However, if the files are typically small this is likely to make the application slower.

public String readFile() {
File f = new File("/Users/Guest/Documents/workspace/Project/src/test.txt");
FileReader fr = null;
BufferedReader br = null;
StringBuilder content = new StringBuilder();;
try {
fr = new FileReader(f);
br = new BufferedReader(fr);
//int c;
//while ((c = fr.read()) != -1) {
//content.append((char) c);
//}
String line = null;
while((line = br.readLine()) != null) {
content.append(line);
}
fr.close();
br.close();
} catch (Exception e) {
// do something
}
return content.toString();
}
Use buffered reader and youll get 70%+ improvement, use string builder instead of string buffer unless you need syncronization.
ran it on a 10MB file 50 times and averaged
no need to put anything that does not need exception handling inside try
no need for that if clause because it will be true only once and so you're wasting time - checking it for every character
there is no runtime exceptions to throw.
results:
fastest combination to slowest:
string builder and buffered reader line by line: 211 ms
string buffer and buffered reader line by line: 213 ms
string builder and buffered reader char by char: 348 ms
string buffer and buffered reader char by char: 372 ms
string builder and file reader char by char: 878
string buffer and file reader char by char: 935 ms
string: extremely slow
so use string builder + buffered reader and make it read line by line for best results.

closing an buffer reader is compulsory

I am trying an example from
http://www.roseindia.net/java/beginners/java-read-file-line-by-line.shtml
in the example the BufferReader is not closed is that necessary to close the BufferReaderor not? Please explain.
FileInputStream fstream = new FileInputStream("textfile.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
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();

Always close streams. It's a good habit which helps you to avoid some odd behaviour. Calling close() method also calls flush() so you don't have do this manually.
The best place where to close streams is probably in a finally block. If you have it like in your example and an exception occurs before the in.close() line, the stream won't be closed.
And if you have chained streams, you can only close the last one and all before it are closed too. This means br.close() in your example - not in.close();
Example
try {
// do something with streams
} catch (IOException e) {
// process exception - log, wrap into your runtime, whatever you want to...
} finally {
try {
stream.close();
} catch (IOException e) {
// error - log it at least
}
}
Alternatively you can use closeQuietly(java.io.InputStream) in Apache Commons library.

From the perspective of resource leak prevention, it is not strictly necessary to close a wrapper stream if you've also closed the stream that it wraps. However, closing the wrapped stream may result in stuff getting lost (specifically in the output case), so it is better to close (just) the wrapper, and rely on documented behavior that the closing the wrapper closes the wrapped stream too. (That is certainly true for the standard I/O wrapper classes!)
Like Peter Lawrey, I question the wisdom of relying on "Rose India" examples. For instance, this one has two more obvious mistakes in it that no half-decent Java programmer should make:
The stream is not closed in a finally block. If any exception is thrown between opening and closing, the in.close() statement won't be executed, and the application will leak an open file descriptor. Do that too often and your application will start throwing unexpected IOExceptions.
The DataInputStream in the chain serves no useful purpose. Instead, they should use fstream as the parameter for the InputStreamReader. Or better still, use FileReader.
Finally, here is a corrected version of the example:
BufferedReader br = new BufferedReader(new FileReader ("textfile.txt"));
try {
String line;
while ((line = br.readLine()) != null) {
// Print the content on the console
System.out.println(line);
}
} finally {
// Close the reader stack.
br.close();
}
or using Java 7's "try with resource":
try (BufferedReader br = new BufferedReader(new FileReader ("textfile.txt"))) {
String line;
while ((line = br.readLine()) != null) {
// Print the content on the console
System.out.println(line);
}
}

Since the underlying stream is closed, it is not absolutely necessary to close BufferedReader, even though it is a good practice to close ALL Closeables in reverse order (relative to the order they were opened in.)