int a = 2, b = 3;
a = a ^ b;
b = a ^ b;
a = a ^ b;
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int a = 1; // 0001
int b = 2; // 0010
int c = 4; // 0100
int d = 8; // 1000
int e = 15;// 1111

// 与运算；0001
System.out.println(Integer.toBinaryString(a & e)); // 0001
// 或运算；0011
System.out.println(Integer.toBinaryString(a | b)); // 0011
// 非运算；0101
System.out.println(Integer.toBinaryString(a ^ c)); // 0101
// 异或运算；...11110111
System.out.println(Integer.toBinaryString(~d));
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public int getBit(int number, int{
    return (number >> bitPosition) & 1;
}
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public int setBit(int number, int{
    return number | (1 << bitPosition);
}
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public int clearBit(int number, int{
    int mask = ~(1 << bitPosition);
    return number & mask;
}
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public int updateBit(int number, int bitPosition, int{
    int clearMask = ~(1 << bitPosition);
    return (number & clearMask) | (bitValue << bitPosition);
}
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public boolean isEven(int{
    return (number & 1) == 0;
}
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public boolean isPositive(int{
    if (number == 0) {
        return false;
    }
    return ((number >> 31) & 1) == 0;
}
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public int multiplyByTwo(int{
    return number << 1;
}
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public int divideByTwo(int{
    return number >> 1;
}
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public int switchSign(int{
    return ~number + 1;
}
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public int multiply(int a, int{
    int multiply = 0;
    while (a != 0 && b != 0) {
        System.out.print("计算步骤(" + (isEven(b) ? "偶数" : "奇数") + ")：a(" + String.format("%04d", Integer.valueOf(Integer.toBinaryString(a))) + ") = " + a + " | b(" + String.format("%04d", Integer.valueOf(Integer.toBinaryString(b))) + ") = " + b);
        // b 是偶数：2a * (b/2)
        if (isEven(b)) {
            a = multiplyByTwo(a);
            b = divideByTwo(b);
        }
        // b 奇数
        else {
            // b 正数：2a * (b - 1)/2 + a
            if (isPositive(b)) {
                multiply += a;
                a = multiplyByTwo(a);
                b = divideByTwo(b - 1);
            }
            // b 负数：2a * (b + 1)/2 - a
            else {
                multiply -= a;
                a = multiplyByTwo(a);
                b = divideByTwo(b + 1);
            }
        }
        System.out.println(" | multiply(" + String.format("%04d", Integer.valueOf(Integer.toBinaryString(multiply))) + ") = " + multiply);
    }
    return multiply;
}
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public int multiplyUnsigned(int number1, int{
    int result = 0;
    int multiplier = number2;
    int bitIdx = 0;
    while (multiplier != 0) {
        if ((multiplier & 1) == 1) {
            System.out.println(number1 + " << " + bitIdx + " = " + (number1 << bitIdx));
            result += number1 << bitIdx;
        }
        bitIdx += 1;
        multiplier = multiplier >> 1;
    }
    return result;
}
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= 16 + 8 + 2
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= 26
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public int countSetBits(int{
    int setBitsCount = 0;
    int number = originalNumber;
    while (number != 0) {
        setBitsCount += number & 1;
        number >>>= 1;
    }
    return setBitsCount;
}
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public int bitsDiff(int number1, int{
    return countSetBits(number1 ^ number2);
}
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public int bitLength(int{
    int bitsCounter = 0;
    while ((1 << bitsCounter) <= number) {
        bitsCounter += 1;
    }
    return bitsCounter;
}
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public boolean isPowerOfTwo(int{
    return (number & (number - 1)) == 0;
}
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public int fullAdder(int a, int{
    int result = 0;
    // 计算每次的进位值，1 + 1 = 0010 进位为1。是一种&运算。
    int carryOut = 0;
    System.out.println("| aBit | bBit | carryIn | aiPlusBi | bitSum | carryOut | result |");
    for (int i = 0; i < 32; i++) {
        int aBit = getBit(a, i);
        int bBit = getBit(b, i);
        int carryIn = carryOut;
        System.out.print("|   " + aBit + "  |  " + bBit + "   |       " + carryIn);
        // 加和 - 两个值；如果相同则为0，不相同则为1
        int aiPlusBi = aBit ^ bBit;
        System.out.print(" |        " + aiPlusBi);
      
        // 加和 - 进位；
        int bitSum = aiPlusBi ^ carryIn;
        System.out.print(" |      " + bitSum);
      
        // 进位；同位置 ai & bi = 1 | 与进位 aiPlusBi & carryIn = 1
        carryOut = (aBit & bBit) | (aiPlusBi & carryIn);
        System.out.print(" |  " + carryOut + "(" + Integer.toBinaryString(carryOut) + ")   ");
      
        // 累加；把当前位置计算的值，左移n位
        result = result | (bitSum << i);
        System.out.println(" | " + result + "(" + String.format("%04d", Integer.valueOf(Integer.toBinaryString(result))) + ")|");
    }
    return result;
}
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