Question

I have this class in Java (it’s from JaCoCo Project):

public class MemoryMultiReportOutput implements IMultiReportOutput {

    private final Map<String, ByteArrayOutputStream> files = new HashMap<String, ByteArrayOutputStream>();

    private final Set<String> open = new HashSet<String>();

    private boolean closed = false;

    public OutputStream createFile(final String path) throws IOException {
        assertFalse("Duplicate output " + path, files.containsKey(path));
        open.add(path);
        final ByteArrayOutputStream out = new ByteArrayOutputStream() {
            @Override
            public void close() throws IOException {
                open.remove(path);
                super.close();
            }
        };
        files.put(path, out);
        return out;
    }

    public void close() throws IOException {
        closed = true;
    }

    public void assertEmpty() {
        assertEquals(Collections.emptySet(), files.keySet());
    }

    public void assertFile(String path) {
        assertNotNull(String.format("Missing file %s. Actual files are %s.",
                path, files.keySet()), files.get(path));
    }

    public void assertSingleFile(String path) {
        assertEquals(Collections.singleton(path), files.keySet());
    }

    public byte[] getFile(String path) {
        assertFile(path);
        return files.get(path).toByteArray();
    }

    public InputStream getFileAsStream(String path) {
        return new ByteArrayInputStream(getFile(path));
    }

    public void assertAllClosed() {
        assertEquals(Collections.emptySet(), open);
        assertTrue(closed);
    }
}

When I compile this class the Eclipse create MemoryMultiReportOutput.class and MemoryMultiReportOutput$1.class.

First question: Why Eclipse create the MemoryMultiReportOutput$1.class? Eclipse considers the ByteArrayOutputStream out a InnerClass?

But my problem is, when I load the MemoryMultiReportOutput.class how can I load the all innerclasses present in parent class?

Answer 1

To answer your first question:

final ByteArrayOutputStream out = new ByteArrayOutputStream() {
        @Override
        public void close() throws IOException {
            open.remove(path);
            super.close();
        }
    };

Here you are creating a subclass of the ByteArrayOutputStream on the fly, i.e anonymous. This is why you have another .class file.

To answer your second question:

You can only load parent inner classes, visible to the subclass, through the Superclass’s instance object :

Superclass s = new Superclass();
Superclass.Subclass sub = s.new Subclass();

If the inner class is static i.e a top-level nested class (since there is no such thing as inner static class) can be instantiated like this:

Superclass.Subclass s = new Superclass.Subclass();

and it does not require an object instance of the superclass.

Hope this helps!