- Generics syntax introduced in Java 1.5 are very difficult to understand and parse when code is read; mixing it with closures will keep the code a little messy;
- People would prefer to do things in the way they are used to, instead of learning a new construct in the language to implement their tasks (it’s better to focus on code maintenance and readability, after all, code is more read than written);
- Anonymous-inner classes are far less readable than inner classes, imagine when closures appear in such a code;
So, I think it’s better to maintain the language with the abstractions it already offers and focus on other improvements, like reifiable generics, that is, making generic type information available at runtime. And you? Will you think useful closures on the Java language?