Answer 1

Integer.parseInt() is used to extract an integer value from a String. I.E. "42"
You can pass a second argument to get a particular radix (base) for that integer string value.
public class Program
{
public static void main(String[] args) {
String num = "42"; // default Decimal base 10
String bin = "101010"; // Binary base 2
String oct = "052"; // Octal base 8 (byte)
String hex = "2A"; // Hexadecimal base 16

System.out.println(Integer.parseInt(num));
System.out.println(Integer.parseInt(bin, 2));
System.out.println(Integer.parseInt(oct, 8));
System.out.println(Integer.parseInt(hex, 16));
}
}
https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#parseInt-java.lang.String-