[grashalm]

Nobody did that because java is a safe language by design. Manual allocation would make it an unsafe language. For the vast majority of applications correctness wins over performance.

Short lived objects are extremely cheap on the JVM with the right GC. Almost stack allocation cheap. So if you write code that avoids too many long lived objects there is almost no overhead to a GC.

For long lived objects GC based compaction can give you even some performance advantage over manual allocation due to better memory locality. But that heavily depends on the application of course.

In my experience people blame the GC way too early. Most often the application is just poorly written and some small tweaks can fix gc spikes.