https://www.topcoder.com/community/data-science/data-science-tutorials/a-bit-of-fun-fun-with-bits/

The basics

At the heart of bit manipulation are the bit-wise operators

• & (and)
• | (or)
• ~ (not)
• ^ (xor)

Operations

• set union
  • A | B
• set intersection
  • A & B
• set subtraction
  • A & ~B
• set negation
  • ALL_BITS ^ A
• set bit, create a 0001000
  • A = A | 1 << bit
• clear bit, create a mask like 1110111
  • A = A & ~(1 << bit)
• test bit / get bit, create a mask like 000100
  • (A & 1 << bit) != 0
• get lowest bit 1 of A
  • A & ~(A - 1)

Find the opposite number

in signed 32-bit integers

int num = 45;
int newNum = ~num + 1;
System.out.println(newNum); //=> -45
int back = ~newNum + 1;
System.out.println(back);//=> 45