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You should be able to simplify this considerably.

I'd suggest using nested loops and putting a single if inside of these loops to determine which type of character to print, as opposed to a series of flat loops that handle each "run" to build a row in multiple steps as you're currently doing.

The "X" star locations are determined by the condition j == i || j == n - i - 1 where i is the current row index and j is the current column index.

For the first and last stars in each row, you can use the condition j == 0 || j == n - 1.

Combining the above four conditions gives a clear way to determine when to print a star or not for each cell.

For example:

public class Main {
    public static void printButterfly(int n) {
        n *= 2;

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (j == 0 || j == i || j == n - i - 1 || j == n - 1) {
                    System.out.print("*");
                }
                else {
                    System.out.print(" ");
                }
            }

            System.out.println();
        }
    }

    public static void main(String[] args) {
        printButterfly(5);
    }
}