Max memory for 64bit Java

Question

What's the maximum amount of heap space that one can allocate for java on a 64-bit platform? Is it unlimited?

Accepted Answer

Theoretically 264, but there might be limitations (obviously)

According to this FAQ it's only limited by memory and swap space on the local system:

On 64-bit VMs, you have 64 bits of addressability to work with resulting in a maximum Java heap size limited only by the amount of physical memory and swap space your system provides.

See also Why can't I get a larger heap with the 32-bit JVM?

Also keep in mind you need to set the max heap via command line. Without an -Xmx command. without it Java uses 64mb + 30% = 83.2mb as a default max heap on 64 bit machines according the same FAQ.

```
java -Xmx1000g myClass 
```

works fine on my machine. But it dosn't seem to yet support the 't' modifier so you can't specify max memory in terabytes yet :)

Max memory for 64bit Java

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