我正在研究snappy、zlib等的压缩器实现（java）。靠近源文件顶部的是下面的这一行。有人能给我解释一下这是什么意思吗？

HACK - Use this as a global lock in the JNI layer
@SuppressWarnings({"unchecked", "unused"})
private static Class clazz = SnappyDecompressor.class;

我知道，例如，在snappy中，snappydecompressor.java本质上是snappyc/本机实现的 Package 器，为了调用该c实现，java层通过jni接口进行调用。
snappy（java Package 器）的源代码snappydecompressor.java的顶部如下：

package org.apache.hadoop.io.compress.snappy;
import java.io.IOException;
import java.nio.Buffer;
import java.nio.ByteBuffer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.compress.Decompressor;

/**
 * A {@link Decompressor} based on the snappy compression algorithm.
 * http://code.google.com/p/snappy/
 */
public class SnappyDecompressor implements Decompressor {
  private static final Log LOG =
      LogFactory.getLog(SnappyCompressor.class.getName());
  private static final int DEFAULT_DIRECT_BUFFER_SIZE = 64 * 1024;

  // HACK - Use this as a global lock in the JNI layer
  @SuppressWarnings({"unchecked", "unused"})
  private static Class clazz = SnappyDecompressor.class;

完整来源