Find Maximum in Java: Solution, Explanation & Practice

Problem summary

Find the maximum value in the array [23, 45, 12, 67, 34].

Starter code

public class Main {
    public static void main(String[] args) {
        int[] arr = {23, 45, 12, 67, 34};
        
        // Find and print maximum
        // Print: Maximum: <result>
    }
}

Expected output and test cases

• Find max value

  Maximum: 67

Hints

1. Start with first element as max
2. Compare each element with current max
3. Update max if element is larger

Validated solution

public class Main {
    static int maximum(int[] values) {
        if (values.length == 0) throw new IllegalArgumentException("array is empty");
        int best = values[0];
        for (int i = 1; i < values.length; i++) {
            if (values[i] > best) best = values[i];
        }
        return best;
    }

    public static void main(String[] args) {
        System.out.println("Maximum: " + maximum(new int[] {23, 45, 12, 67, 34}));
    }
}

How to approach the problem

Use the first value as the current maximum, then replace it only when a larger value appears. This works for all-negative arrays; an arbitrary starting value such as zero does not.

Approach

1. Reject an empty array or return an optional result.
2. Seed best with the first array value.
3. Compare every later value against best.

Time and space complexity

Time: O(n). Space: O(1).

Edge cases to test

• All values may be negative.
• Repeated maxima do not need special handling when only the value is requested.

Common mistakes

• Starting best at 0.
• Reading values[0] before deciding what an empty input means.

Follow-up challenge

Return the first index of the maximum too, with a documented tie rule.

Related Arrays exercises

• Practice Declare and Print Array in Java
• Practice Sum of Array in Java
• Practice Calculate Average in Java

Practice all Arrays exercises · Run this idea in the Java compiler