Try adding an integer, a floating point and a double-precision number. What will you get? Still reporting an error?
Integer and floating point both become double, and the result is also double.
int a = 1；
Floating point b = 2；;
Double c = 2.3
Double d = 0；;
d = a+b+c；
system . out . print(d)；
//The result is 5.3.