Backward compatibility - you could run an application that uses generics, introduced in Java 1.5, on a Java 1.4 VM. At the time that was pretty amazing. These days, with so many backward compatibility-breaking changes being introduced, it doesn't feel so great.

That was the original plan, but it never worked in my experience. The compiler as shipped required that -source 1.5 use -target 1.5. So hobbling the language this way served no benefit in the end.

Btw, type erasure is only a problem for Java because it supports runtime type information (which is incomplete, because of type erasure), and overloading (which I have no idea why the compiler can't handle). For languages like ML and Haskell, type erasure is no problem, because you can't access the types at runtime anyways.

In my opinion, no it really isn't. You can just create a method with a different name or a static constructing method if you need to overload constructors.

The major pain point with generics is that they don't work with primitives.