Declaring a RandomAccessFile object inside a try block gives resource leak warning but declaring it outside does not?

Question

This is my code:

try {
    RandomAccessFile srcFile = new RandomAccessFile("src.txt", "rw");
} catch(FileNotFoundException e) {
    e.printStackTrace();
}

This code gives me a warning that the RandomAccessFile object srcFile is never closed.

But if I modify my code and declare the srcFile outside the try block (as in the code below), the warning goes away.

RandomAccessFile srcFile;
try {
    srcFile = new RandomAccessFile("src.txt", "rw");
} catch(FileNotFoundException e) {
    e.printStackTrace();
}

Why does this happen, since I'm not doing srcFile.close(); in any case?

score 2 · Accepted Answer · answered May 13 '15 at 13:47

Extract from this:

If a resource is stored in a field, no single method is considered as responsible for closing; no problem is reported.

I assume this is what is happening when declaring srcFile outside of the scope of the try. This implies that eclipse compiler cannot assume that the resource needs to be closed, because I may still be referenced outside of the scope in was created in.

Since JDK 1.7 you can solve this with try-with-resources:

try (RandomAccessFile srcFile =  new RandomAccessFile("src.txt", "rw")) {
    //Do something with srcFile
} catch(IOException e) {
    e.printStackTrace();
}

Note that srcFile will be closed automatically after the try has been executed.

Declaring a RandomAccessFile object inside a try block gives resource leak warning but declaring it outside does not?

1 Answers1