如何将负数作为二进制分配给java中的int变量？

Question

I was seeing how to represent binary numbers in java. one option is to use as String and use Integer.parseInt() to get the decimal value;

The other option (assignment of 2 to b ):

int b = 0b0010; //2
System.out.println(b);
System.out.println(Integer.toBinaryString(-2));

output:

2
11111111111111111111111111111110

using this format, how to represent -2:

int c=??//-b

Answer 1

int values are stored in 32 bits where the most significant bit is the sign.

0b0010; //2

is actually

0b00000000_00000000_00000000_00000010; //2

To convert that to a negative number, you flip the 0 s to 1 s and the 1 s to 0 s` and add 1. So

0b00000000_00000000_00000000_00000010; //2
0b11111111_11111111_11111111_11111101
0b11111111_11111111_11111111_11111110; // +1

And so

int b = 0b11111111_11111111_11111111_11111110;

would have the value -2 .

Answer 2

Use the Bitwise NOT operator:

00000000000000000000000000000010 // 2 = 0b0010
00000000000000000000000000000001 // 1 = 0b0010-0b0001
11111111111111111111111111111110 // ~1 = ~(0b0010-0b0001)

11111111111111111111111111111110 // -2 = ~(0b0010-0b0001)

So you just subtract 0b001 and flip all the bits with the ~ Bitwise operator:

int b = ~(0b0010-0b0001); // ~(2-1) = ~1 = -2
System.out.println(b);
System.out.println(Integer.toBinaryString(b));

Demo

Answer 3

You are confusing storage with presentation. int b has no base, regardless of whether you assign 2 , 0b010 or 0x02 to it. Base 10 is just something println assumes.

You can use Integer.toString(number, radix) to print properly signed binary numbers.