Default values in Java - Time & Space Complexity

Time Complexity: Default values

O(n)

Understanding Time Complexity

We want to see how the time it takes to run code changes when using default values in Java.

Specifically, we ask: does setting default values affect how long the program runs as input grows?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

public class DefaultValues {
    public static void fillArray(int[] arr) {
        for (int i = 0; i < arr.length; i++) {
            arr[i] = 0; // default value
        }
    }
}
    

This code fills an array with the default value 0 by looping through each element.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The for-loop that sets each array element to 0.
• How many times: It runs once for each element in the array, so as many times as the array length.

How Execution Grows With Input

As the array gets bigger, the number of steps grows in a straight line.

Input Size (n)	Approx. Operations
10	10 steps
100	100 steps
1000	1000 steps

Pattern observation: If you double the array size, the work doubles too.

Final Time Complexity

Time Complexity: O(n)

This means the time to fill the array grows directly with the number of elements.

Common Mistake

[X] Wrong: "Setting default values is instant and does not depend on array size."

[OK] Correct: Each element must be set one by one, so the time grows with the array length.

Interview Connect

Understanding how loops over arrays affect time helps you explain code efficiency clearly and confidently.

Self-Check

"What if we used a built-in method like Arrays.fill instead of a loop? How would the time complexity change?"