一个引用一个对象在32位JVM（至少​​在热点）都将占用4字节。

A reference to an Object on a 32 bit JVM (at least on Hotspot) takes up 4 bytes.

请问64位的热点JVM需要8个字节？或者是一些巧妙的融为一体pression怎么回事？ 如果不是这样，每个对象[] 将需要两倍的堆内存，我不知怎么想（希望，期待）是不是这样的。

Does the 64 bit Hotspot JVM need 8 bytes? Or is some clever compression going on? If not, every Object[] would require twice as much heap memory, which I somehow think (hope, expect) is not the case.

更新/额外的问题：这是否真的很重要，或者这是一个微不足道的增加，因为多数引用指向，比几个字节的更大的（而有人可能会争辩说，这些对象是对象又主要包含对其他对象的）？

Update/extra question: Does this really matter, or is this a negligible increase, because most references point to objects that are much larger than a few bytes (whereas one might argue that those objects are in turn mostly comprised of references to other objects)?

推荐答案

在64位系统中，对象引用通常是8个字节。但在来自Sun /甲骨文最近的JVM可以启用的COM pressed哎呀，从而降低参考大小为4字节的上堆大小较小的限制成本。

In a 64-bit system, object references are typically 8-byte long. But in recent JVMs from Sun/Oracle you can enable Compressed Oops, which reduce reference size to 4 bytes at the cost of a smaller limit on heap size.