它将返回不可清除的字节数，如果操作成功，则返回0。

It returns the number of bytes that were not clearable or zero if the operation was successful.

youdao

由 -XX:+UseParallelGC 启用的并行清除收集器是年轻代收集器，针对多处理器系统上非常大(吉字节以及更大的)堆进行了优化。

The parallel scavenging collector, enabled by -XX:+UseParallelGC, is a young-generation collector optimized for very large (gigabyte and larger) heaps on multiprocessor systems.

youdao