通过位运算实现两个数的加、减、乘、除

//通过位运算实现两个数的加、减、乘、除
public class BitSuan{

//(1)加法运算
public static int add(int a,int b)
{
int sum=a;
while(b!=0)
{
//a与b无进位相加
sum=a^b;
b=(a&b)<<1;
a=sum;
}
return sum;

}
//负数按位置取反+1
public static int negNum(int n)
{
return add(~n,1);
}
//(2)减法运算
public static int minus(int a,int b)
{
return add(a,negNum(b));
}
//(3)乘法运算
public static int multi(int a, int b) {
int res = 0;
while (b != 0) {
if ((b & 1) != 0) {
res = add(res, a);
}
a <<= 1;
b >>>= 1;
}
return res;
}
//判断是否是负数
public static boolean isNeg(int n) {
return n < 0;
}

public static int div(int a, int b) {
int x = isNeg(a) ? negNum(a) : a;
int y = isNeg(b) ? negNum(b) : b;
int res = 0;
for (int i = 31; i > -1; i = minus(i, 1)) {
if ((x >> i) >= y) {
res |= (1 << i);
x = minus(x, y << i);
}
}
return isNeg(a) ^ isNeg(b) ? negNum(res) : res;
}
//(4)除法运算
public static int divide(int a, int b) {
if (b == 0) {
throw new RuntimeException("divisor is 0");
}
if (a == Integer.MIN_VALUE && b == Integer.MIN_VALUE) {
return 1;
} else if (b == Integer.MIN_VALUE) {
return 0;
} else if (a == Integer.MIN_VALUE) {
int res = div(add(a, 1), b);
return add(res, div(minus(a, multi(res, b)), b));
} else {
return div(a, b);
}
}

public static void main(String[]args)
{
int a=10;
int b=5;
System.out.println(add(a,b));
System.out.println(minus(a,b));
System.out.println(multi(a,b));
System.out.println(divide(a,b));

}
}