jasonqu/map type check difference in java and scala

## map type check difference in java and scala
// in scala, map type error could be check in compile time
val map = Map(1 -> "a")
map.get("a")

// in java, it cannot
Map<Integer, String> map = new HashMap<>();
map.put(1, "a");
map.get("a");
	// in scala, map type error could be check in compile time
	val map = Map(1 -> "a")
	map.get("a")

	// in java, it cannot
	Map<Integer, String> map = new HashMap<>();
	map.put(1, "a");
	map.get("a");