First, the automatic conversion
The purpose type is larger than the original type, the two data types are compatible with each other.
byte--->short
short--->int
char--->int
int--->long/double
float--->double
If there is a double, the other is converted to double, double result is two numbers.
Otherwise, the two numbers is a float, the other is converted to float
Otherwise, if there is a long-type two operands, it is converted into another type long
Otherwise, the two numbers are converted to an int
Second, the cast
:( syntax conversion of data types) variables need to convert
Float transferred to integer - the number of decimal places amputated, reserved integer
Long integer assigned to bit short integer ---
