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Calculate Power Without Math.pow() in Java

intermediate· Control Flow · Loops

Problem

Raising a number to a whole-number exponent is just multiplying the base by itself that many times, which a loop can do directly without any built-in power function.

Given a base and a non-negative integer exponent, calculate the base raised to that exponent.

Input

base = 2, exponent = 10

Output

2^10 = 1024

Java Program

Java

public class PowerWithoutMathPow {
    public static void main(String[] args) {
        int base = 2, exponent = 10;
        long result = 1; // base^0 is 1, so this is correct even before the loop runs

        for (int i = 0; i < exponent; i++) {
            result *= base;
        }

        System.out.println(base + "^" + exponent + " = " + result);
    }
}

▶ Run Code

Output

2^10 = 1024

Core Logic

Multiplying a running result by the base once per unit of exponent builds up the power one factor at a time.

How It Works

1result starts at 1, the correct answer for any base raised to the power of 0.
2The loop runs exactly exponent times, multiplying result by base on each pass.
3By the time the loop ends, result holds base multiplied by itself exponent times.

For base = 2 and exponent = 10, the loop multiplies by 2 ten times, building result up to 1024.

💡

Key Point: Starting result at 1 — not 0 or base — is what makes an exponent of 0 correctly fall out to 1 without any special case.

Complexity

Time Complexity: O(exponent)Space Complexity: O(1)

Why: The loop multiplies the running result by the base once per unit of exponent, and keeps only that single running value.

Key Concepts

for looprunning productexponentiation

Approach 2: Java 8

Java

import java.util.stream.IntStream;

public class PowerWithoutMathPowStream {
    public static void main(String[] args) {
        int base = 2, exponent = 10;
        // Reduces exponent elements down to a single running product, multiplying by base each time
        long result = IntStream.rangeClosed(1, exponent).reduce(1, (a, b) -> a * base);
        System.out.println(base + "^" + exponent + " = " + result);
    }
}

▶ Run Code

Output

2^10 = 1024

Core Logic

The same repeated multiplication is exactly what Stream's reduce() is built for — folding the base into a running product one step at a time.

How It Works

1IntStream.rangeClosed(1, exponent) generates exactly exponent values, one per multiplication needed.
2.reduce(1, (a, b) -> a * base) starts the running product at 1 and multiplies it by base once per element in the stream.
3The second argument b is never actually used — the stream's only job here is to trigger the right number of multiplications.

For base = 2 and exponent = 10, the stream reduces ten times, each multiplying by 2, landing on the same 1024.

💡

Key Point: Using a long for the running product keeps this safe from overflow even for larger bases and exponents than this example needs.

Complexity

Time Complexity: O(exponent)Space Complexity: O(1)

Why: reduce() still performs one multiplication per unit of exponent, carrying forward a single running long value.

Key Concepts

StreamIntStream.rangeClosed()reduce()

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