Check that a String entered contains only 1's and 0's

Question

I am writing a program that switches a binary number into a decimal number and am only a novice programmer. I am stuck trying to determine that the string that was entered is a

Answer 1

You could just use a regular expression:

num.matches("[01]+")

This will be true if the string num contains only 0 and 1 characters, and false otherwise.

Answer 2

n!=1 || n!=0 is always true because you cannot have n = 0 and 1 at the same moment. I guess you wanted to write n!=1 && n!=0.