This is possible exactly because Java is statically-typed. Java's type system works over the operands, and does implicit conversions before the expression gets a chance to run. It sees values and does implicit magic from left to right.

Python, on the other hand, does not need to do a typing pass at parse-time. Instead, literals are stored as values, and those values are tagged with their source class. Python's way of doing it means that a + operation is called upon with an integer and a string.

Java might be able to yield the same kind of result as Python if it had operator overloading. It could define Integer's + operator as only taking other Integer values, therein yielding a type error at parse-time.

My own language uses ++ instead of + to distinguish between addition and concatenation, though I've considered some other token since the two are quite similar to each other.