# Java Program to Calculate the Power of a Number

In this program, you'll learn to calculate the power of a number with and without using pow() function.

## Example 1: Calculate power of a number using a while loop

``````public class Power {

public static void main(String[] args) {

int base = 3, exponent = 4;

long result = 1;

while (exponent != 0)
{
result *= base;
--exponent;
}

}
}``````

When you run the program, the output will be:

`Answer = 81`

In this program, base and exponent are assigned values 3 and 4 respectively.

Using the while loop, we keep on multiplying result by base until exponent becomes zero.

In this case, we multiply result by base 4 times in total, so result = 1 * 3 * 3 * 3 * 3 = 81.

## Example 2: Calculate power of a number using a for loop

``````public class Power {

public static void main(String[] args) {

int base = 3, exponent = 4;

long result = 1;

for (;exponent != 0; --exponent)
{
result *= base;
}

}
}``````

When you run the program, the output will be:

`Answer = 81`

Here, instead of using a while loop, we've used a for loop.

After each iteration, exponent is decremented by 1, and result is multiplied by base exponent number of times.

Both programs above doesn't work if you have a negative exponent. For that, you need to use pow() function in Java standard library.

## Example 3: Calculate the power of a number using pow() function

``````public class Power {

public static void main(String[] args) {

int base = 3, exponent = -4;
double result = Math.pow(base, exponent);

`Answer = 0.012345679012345678`
In this program, we use Java's `Math.pow()` function to calculate the power of the given base.