Integer.valueOf 不适用于 Java 中 -1 的二进制表示

Question

The following code attempts to output to obtain -1 from its 2's complement binary representation, but gives a NumberFormatException.

System.out.println(Integer.parseInt(Integer.toBinaryString(-1), 2));  //Raises Exception

System.out.println(Integer.valueOf("11111111111111111111111111111111", 2));  //Raises Exception

Infact Integer.valueOf doesn't seem to work for any signed negative number's binary representation. Why is the code outputting error?

Answer 1

valueOf doesn't know about 2's complement, so it thinks you are asking to covert an unsigned value in base 2 that is too large to fit in an int. (Try removing one of the 1 's.)