Is there a specific reason why Java does not have an in-built external sort algorithm implemented ?
Because the JDK contains only the mostly used components.
It is the same thing with any external framework content. Why isn't it directly built-in ?
Simply because it doesn't need to be built-in. And because it's not developed by the same people.
But still you can use an external framework, or a library which will help you with that.
Resources :