Why can't we use #,@ in variable names?

Question

*, +, -, &, ^, . can't be used because they are used in java as operators or separators. But what about these characters?

Answer 1

There is certain rules to use variable name...
1.variable name must be a letter, underscore, dollor.
2.number are not allowed as the first character.
3.must not include mathematical and logical operators.
4.must not contain spaces.

Answer 2

we can just use $