Do unclosed streams cause memory leaks in java?

Question

I believe open streams cause memory leak in java (at least java 1.6 and earlier did had this problem).

But, while searching (even here), I found some people agreeing with this while others do not. So, if I write this program:

import java.io.*;
public class CreatingMemoryLeak {

    public static void main(String args[])
    {
        String s = "xxxxxxx";
        InputStream in = new ByteArrayInputStream(ss.getBytes());
        BufferedInputStream bf = new BufferedInputStream(in);

        try {
            while(bf.read()>0)
            {
                System.out.println("got it");
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("Here is a input stream " + s +" causing a memory leak");

    }
}

and if I do not close the bf stream explicitly, will it cause a memory leak?

Answer 1

It's important to be precise in the use of the term 'memory leak' with respect to Java.

In Java, a memory leak happens when your code holds a reference permanently, so that some object is never garbage collected.

Failing to close a stream is not a memory leak in this sense. Streams that have native resources have finalizers; the GC will eventually close them down. Unless you hold a reference to the unclosed stream it isn't a leak.

However, there are other kinds of leaks besides memory leaks. Most operating systems limit the number of open files. If you fail to close your streams, the GC may take a very long time to close them for you; the net result may be that you run out of system file descriptors and your code fails to open one more file. Some people will call this a leak, but it's not accuracy to call it a memory leak.