Unassigned closeable stream

Question

I'm working with Eclipse Juno and as I'm writing the following code, Eclipse warns me about a possible memory leak :

String s = new Scanner( System.in ).nextLine();

Indeed, I never close the System.in stream. How does the JVM (jre7) handle this ? Is it a good use ?

Answer 1

This is a false alarm, I believe. Eclipse is confusing it with something like this:

String s = new Scanner(new FileReader("foo.txt")).nextLine();

which does leak a new Closeable each time you execute it.

But in your code, the underlying stream (System.in) is still reachable and usable. Certainly, there is no need to close it from the "resource leakage" perspective.

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Indeed, I never close the System.in stream. How does the JVM (jre7) handle this ?

The System.in stream remains open until (presumably) the application exits. But that is no different to the situation if you hadn't called new Scanner(System.in) in the first place.