Java 7 diamond operator: why was it difficult to implement?

Question

I watched the Oracle OTN Virtual Event: Java SE and JavaFX 2.0 (28 Feb 2012) and while talking about the new diamond operator (that Map&g

Answer 1

Something which Java doesn't do (which many languages have) is implied types based on usage. i.e. Java doesn't imply a require type based on how it is used.

e.g.

 Type a = b;

The type of a and the type of b are independent and no assumptions are made about b based on the type of a.

MethodHandles are showing signs of supporting this. The return type use can be based on context, but this is a runtime feature.

In conclusion, my assumption is; It was hard to implement in Java because the language didn't support any like it. If the language used feature like this all the time, the approach to take would be understood (in term of defining a spec of how it should work) and supported by the tools in the compiler.