在java或其他gc-lang中取消關閉資源會被gc自動關閉嗎？ 為什么

Question

諸如 fileInputStream 之類的資源未關閉。 gc清理時會關閉嗎？ 為什么或為什么不呢？

Answer 1

指的是： Java中的finalize()方法是什么時候調用的？

FileInputStream覆蓋Object#finalize ，如下所示：

/**
 * Ensures that the <code>close</code> method of this file input stream is
 * called when there are no more references to it.
 *
 * @deprecated The {@code finalize} method has been deprecated.
 *     Subclasses that override {@code finalize} in order to perform cleanup
 *     should be modified to use alternative cleanup mechanisms and
 *     to remove the overriding {@code finalize} method.
 *     When overriding the {@code finalize} method, its implementation must explicitly
 *     ensure that {@code super.finalize()} is invoked as described in {@link Object#finalize}.
 *     See the specification for {@link Object#finalize()} for further
 *     information about migration options.
 *
 * @exception  IOException  if an I/O error occurs.
 * @see        java.io.FileInputStream#close()
 */
@Deprecated(since="9")
protected void finalize() throws IOException {
    if ((fd != null) &&  (fd != FileDescriptor.in)) {
        /* if fd is shared, the references in FileDescriptor
         * will ensure that finalizer is only called when
         * safe to do so. All references using the fd have
         * become unreachable. We can call close()
         */
        close();
    }
}

當FileInputStream#finalize被調用時， FileInputStream#close將被調用（在某些條件下）。 然而， Object#finalize已棄用Java中9，所以應該不能依賴。 您應該始終關閉流以防止內存泄漏，即使底層垃圾收集可能會為您處理。