Switch (E)

1. Switch (e) {} ecannot be of the float type. Why?
It cannot be float, it can be an int, or it can be converted to an integer string, Boolean, or enumeration type. The syntax is designed in this way. Otherwise, switch expression not integral and an error is returned!
Cause: the condition of the switch can only be equal to or equal, so the data type has a high precision requirement. String, Boolean, and enumeration types can all be converted to Integers for judgment, because the integer has a great degree of certainty on equality and inequality, while float and double represent decimal places, after all, the accuracy is limited. If the accuracy is equal to or not equal to the value of a computer after the limit is exceeded, it cannot be determined, so it cannot be used.