Question

Java Special Methods:

A) Write a method that finds the maximum of two numbers. You should not use if-else or any other comparison operator.

B) Write methods to implement the multiply, subtract and divide operations for integers. The results of all of these are integers. Use only the add operator.

Answer 1

Answer A:

Answer B:

static int flipSign(int a)
{
int neg = 0;
  
// If sign is + ve turn it -ve
// and vice-versa
int tmp = a < 0 ? 1 : -1;
while (a != 0)
{
neg += tmp;
a += tmp;
}
return neg;
}
  
// Check if a and b are of different signs
static boolean areDifferentSign(int a, int b)
{
return ((a < 0 && b > 0) || (a > 0 && b < 0));
}
  
// Function to subtract two numbers
// by negating b and adding them
static int sub(int a, int b)
{
// Negating b
return a + flipSign(b);
}
  
// Function to multiply a by b by
// adding a to itself b times
static int mul(int a, int b)
{
// because algo is faster if b<a
if (a < b)
return mul(b, a);
  
// Adding a to itself b times
int sum = 0;
for (int i = Math.abs(b); i > 0; i--)
sum += a;
  
// Check if final sign must be -ve or + ve
if (b < 0)
sum = flipSign(sum);
  
return sum;
}
  
// Function to divide a by b by counting   
// how many times 'b' can be subtracted   
// from 'a' before getting 0
static int division(int a, int b)
{
// Raise exception if b is 0
if (b == 0)
throw new ArithmeticException();
  
int quotient = 0, dividend;
  
// Negating b to subtract from a
int divisor = flipSign(Math.abs(b));
  
// Subtracting divisor from dividend
for (dividend = Math.abs(a); dividend >= Math.abs(divisor);
dividend += divisor)
quotient++;
  
// Check if a and b are of similar symbols or not
if (areDifferentSign(a, b))
quotient = flipSign(quotient);
return quotient;
}
  
// Driver code
public static void main(String[] args)
{
System.out.println("Subtraction is " + sub(4, -2));
System.out.println("Product is " + mul(-9, 6));
  
try
{
System.out.println("Division is " + division(8, 2));
}
  
catch (ArithmeticException e)
{
System.out.println("Exception :- Divide by 0");
}
}
}