Is it necessary to close a FileWriter, provided it is written through a BufferedWriter? [duplicate]

Question

Consider a BufferedReader as below:

writer = new BufferedWriter(new FileWriter(new File("File.txt"), true));

In this case at the end of the application, I am closing the writer with writer.close()

Will this be enough? Won't that FileWriter created with new FileWriter(new File("File.txt"), true) need to be closed?

Holocrine

Answer 1

It is not necessary to close it, because BufferedWriter takes care of closing the writer it wraps.

To convince you, this is the source code of the close method of BufferedWriter:

public void close() throws IOException {
    synchronized (lock) {
        if (out == null) {
            return;
        }
        try {
            flushBuffer();
        } finally {
            out.close();
            out = null;
            cb = null;
        }
    }
}

Estelaestele

The out.close(); line is missing in the Java 8 BufferedWriter – Gisellegish

@A.Roshenko look closely, the try block has been replaced with try-with block in java 8 BufferedReader. So, same thing, underlying writer is still being closed in java 8 as well. – Mccullum

Why do we need to call out.close() explicitly? Why wouldn't the BufferedWriter's destructor flush the buffer automatically? – Selfpropelled

Answer 2

Yes writer.close() closes underlying writers/streams as well.

Alphaalphabet

Answer 3

It is better to close each open stream individually as all are separate stream. If there are some error occurs in nested stream, then stream won't get close. So its better to close each nested stream exclusively.

For more details refer following link:

Correct way to close nested streams and writers in Java

Nodular

Thanks for linking in this question. But I disagree that it's any better to close the inner writers as well, because: 1) the finally clause (as you see in my answer) guarantees that the inner writer's close method is called 2) In the (rare) case that out.close() might throw an exception, the writer's member variables out and cb are not set to null, which is no problem because they are plain objects (not system resources, like e.g. a file handle) – Estelaestele

Answer 4

You need to close the outermost streams only. rest of the streams are temporary and will be closed automatically. if you create the streams separately and then nested them, in that case you need to close the individual stream. Check this Question also Correct way to close nested streams and writers in Java

Infra

No, you don't 'need to close the individual stream[s]'. You only need to close the outermost stream. – Ptosis