public class DirectMemoryTest {
    public static void main(String[] args) {
        ByteBuffer byteBuffer = ByteBuffer.allocateDirect(1024);
        Object obj = new Object();
        obj = null;
        byteBuffer = null;
        //Full GC (System.gc()),obj被回收,byteBuffer不会被回收
        System.gc();
        System.out.println(byteBuffer);
    }
}
复制

可以看到full gc日志.Object被回收,DirectByteBuffer却不能被回收.是哪方面原因呢？JNI,虚引用？还是JVM有什么不为人知的处理。