```java
public class LinearSearch {
    // Method that performs linear search
    public static int linearSearch(int[] array, int target) {
        // Iterate through each element in the array
        for (int i = 0; i < array.length; i++) {
            // If current element matches target, return its index
            if (array[i] == target) {
                return i;
            }
        }
        // If target is not found, return -1
        return -1;
    }

    // Main method to test the linear search
    public static void main(String[] args) {
        // Test array
        int[] numbers = {4, 2, 7, 1, 9, 5, 3, 8, 6};
        
        // Test cases
        int target1 = 7;  // exists in array
        int target2 = 10; // doesn't exist in array
        
        // Search for target1
        int result1 = linearSearch(numbers, target1);
        if (result1 != -1) {
            System.out.println("Element " + target1 + " found at index " + result1);
        } else {
            System.out.println("Element " + target1 + " not found in array");
        }
        
        // Search for target2
        int result2 = linearSearch(numbers, target2);
        if (result2 != -1) {
            System.out.println("Element " + target2 + " found at index " + result2);
        } else {
            System.out.println("Element " + target2 + " not found in array");
        }
    }
}
```