# 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

1. public class Power {
2. public static void main(String[] args) {
3. int base = 3, exponent = 4;
4. long result = 1;
5. while (exponent != 0)
6. {
7. result *= base;
8. --exponent;
9. }
10. System.out.println("Answer = " + result);
11. }
12. }

When you run the program, the output will be:

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

1. public class Power {
2. public static void main(String[] args) {
3. int base = 3, exponent = 4;
4. long result = 1;
5. for (;exponent != 0; --exponent)
6. {
7. result *= base;
8. }
9. System.out.println("Answer = " + result);
10. }
11. }

When you run the program, the output will be:

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

1. public class Power {
2. public static void main(String[] args) {
3. int base = 3, exponent = -4;
4. double result = Math.pow(base, exponent);
5. System.out.println("Answer = " + result);
6. }
7. }

When you run the program, the output will be: