 # 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.

To understand this example, you should have the knowledge of the following Java programming topics:

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

``````class Main {
public static void main(String[] args) {

int base = 3, exponent = 4;

long result = 1;

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

}
}``````

Output

`Answer = 81`

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

Using the while loop, we keep on multiplying the result by base until the 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 the power of a number using a for loop

``````class Main {
public static void main(String[] args) {

int base = 3, exponent = 4;

long result = 1;

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

}
}``````

Output

`Answer = 81`

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

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

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

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

``````class Main {
public static void main(String[] args) {

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

}
}``````

Output

`Answer = 0.012345679012345678`

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

We can also compute the power of a negative number using the `pow()` method.

## Example 4: Compute Power of Negative Number

``````class Main {
public static void main(String[] args) {

// negative number
int base = -3, exponent = 2;

double result = Math.pow(base, exponent);
`Answer = 9.0`
Here, we have used the `pow()` method to compute the power of a negative number -3.