[organsnyder]

I think a lot of it was for performance concerns. For math-heavy operations, the dealing with lots of objects caused quite a bit of garbage collection overhead. This is much less important now—they've optimized garbage collection to the point that it is often irrelevant—but it's still a concern in math-heavy applications.

Here's an article that goes into it in more detail: http://www.javaworld.com/article/2150208/java-language/a-cas...