gistfile1.java

import java.io.Closeable;
import java.io.IOException;
import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

public class Resource
{
    private Reference resourceReference;

    public Resource(Reference resourceReference)
    {
        this.resourceReference = checkNotNull(resourceReference, "resourceReference is null");
    }

    public Closeable getResource()
    {
        return resourceReference.getResource();
    }

    public static class Reference
            extends PhantomReference<Resource>
    {
        private final Closeable resource;

        public Reference(Resource referent, ReferenceQueue<Resource> queue, Closeable resource)
        {
            super(referent, queue);
            this.resource = resource;
        }

        public void destroy()
        {
            try {
                resource.close();
            }
            catch (IOException e) {
                // ignored
            }
        }

        public Closeable getResource()
        {
            return resource;
        }
    }
}