How to convert a Binary String to a base 10 integer in Java

Question

I have an array of Strings that represent Binary numbers (without leading zeroes) that I want to convert to their corresponding base 10 numbers. Consider:

bi         


        

Answer 1

I love loops! Yay!

String myString = "1001001"; //73

While loop with accumulator, left to right (l doesn't change):

int n = 0,
    j = -1,
    l = myString.length();
while (++j < l) n = (n << 1) + (myString.charAt(j) == '0' ? 0 : 1);
return n;

Right to left with 2 loop vars, inspired by Convert boolean to int in Java (absolutely horrible):

int n = 0,
    j = myString.length,
    i = 1;
while (j-- != 0) n -= (i = i << 1) * new Boolean(myString.charAt(j) == '0').compareTo(true);
return n >> 1;

A somewhat more reasonable implementation:

int n = 0,
    j = myString.length(),
    i = 1;
while (j-- != 0) n += (i = i << 1) * (myString.charAt(j) == '0' ? 0 : 1);
return n >> 1;

A readable version :p

int n = 0;
for (int j = 0; j < myString.length(); j++) {
    n *= 2;
    n += myString.charAt(j) == '0' ? 0 : 1;
}
return n;