如何在Android中进行1的补码和加1？

Question

I am develop an application in Android . I receive the value from network and convert it by 1's complement.

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For Example :

The value is 247 .

I convert the 247 to the binary: 1111 0111

After the 1's complement add 1 , the value is 0000 1001 .

Turn the the value 0000 1001 to the Decimal is 9 .

It mean the -9 in my application , and that is the value what I want.

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I try to use Integer.toBinaryString for convert the 247 to the 1111 0111 . And use for loop to convert the 0 to 1 and 1 to 0 . But it seems not a good method...

What should I do to implement the above example ?

Answer 1

Multiply by -1

2's complement already means ADD 1. If you just invert the number it is called 1's complement.

But the numbers are stored in binary already. If you get the number 247 it means you are treating it as UNSIGNED and you want to treat it as SIGNED. If it is 8 bits, treat it as a 'signed char'