Math.max and min

Two numbers are different—one is larger and the other is smaller. With Math.max we get the larger one, and with Math.min we get the smaller one.

With these methods, we can restrict numbers to a valid range. We can avoid accessing an array out of range. We can keep track of the highest (or lowest) score.

First example

Here we use Math.min. We pass it two arguments and receive the argument back that is lower. We use Math.min to avoid accessing an array at an index that is too high.

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

        String[] animals = { "cat", "dog", "bird" };

        // Use Math.min to keep index in range.
        // ... Try to get index 4.
        String result = animals[Math.min(animals.length - 1, 4)];
        System.out.println(result);

        // Try to get index 1.
        result = animals[Math.min(animals.length - 1, 1)];
        System.out.println(result);
    }
}
bird
dog

Array for-loop

In this example we have two arrays: one has 3 elements, the other 4. With Math.min we get the count of common element indexes in both arrays.

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

        int[] codes1 = { 100, 200, 300 };
        int[] codes2 = { 300, 400, 500, 600 };

        // Use Math.min to get smallest length for both arrays.
        int commonLength = Math.min(codes1.length, codes2.length);

        // Display elements in each array at indexes.
        // ... All indexes have elements.
        for (int i = 0; i < commonLength; i++) {
            System.out.println(codes1[i] + "/" + codes2[i]);
        }
    }
}
100/300
200/400
300/500

Math.max

In this example we score words based on their letters. We use Math.max to keep track of the highest-scoring word. We do not need if-statements to track this value.

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

        String[] codes = { "abc", "def", "abcdef", "bc" };

        // Loop over strings and score them on their letters.
        int maxScore = -1;
        for (String code : codes) {
            // Compute score for the string.
            int score = 0;
            for (int i = 0; i < code.length(); i++) {
                score += code.charAt(i);
            }
            System.out.println(score);
            // Keep track of highest score with Math.max.
            maxScore = Math.max(maxScore, score);
        }

        // Print highest score.
        System.out.println("Max score: " + maxScore);
    }
}
294
303
597
197
Max score: 597

A review

With Math.max and Math.min we compare two numbers in a method call. We can avoid writing many if-statements. This leads to clearer, more correct, more declarative code.