Question

i have code that looks like this

             public static void main(String[] args) {
    String string= "11011100010000010001000000000000";
   String string1= "00000000010000110000100000101100";

    System.out.println(Integer.toHexString(Integer.parseInt(string1,2)));

    System.out.println(Integer.toHexString(Integer.parseInt(string,2)));


}

the first string convert just fine but the second one has an error of java.lang.NumberFormatException
dont know what the problem is

Answer 1

When the most significant bit of a 32-character binary number is set to 1, the resultant value exceeds the range of positive numbers supported by int, and can no longer be interpreted as a valid integer number. This causes the exception according to the documentation:

An exception of type NumberFormatException is thrown if any of the following situations occurs:

• The first argument is null or is a string of length zero.
• The radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.
• Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign ‘-‘ (‘\u002D’) provided that the string is longer than length 1.
• The value represented by the string is not a value of type int. (emphasis is mine)

In order to enter this negative binary value, use - sign in front of your number, and convert the remaining bits to 2-s complement representation.

If you need numbers that are longer than 32 bits, or if you would like the value to continue being interpreted as a positive number, you would need to switch to the 64-bit integer data type.