https://www.acmicpc.net/problem/10996

별 찍기 - 21.java

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        StringBuilder sb = new StringBuilder();
        int n = sc.nextInt();
        for(int i=0; i<n; i++){
            if (n==1) {
                sb.append("*");
                break;
            }
            for(int j=0; j<2; j++){
                for(int k=0; k<n; k++){
                    if(j==0 && k%2==0 || j==1 && k%2==1) sb.append("*");
                    else sb.append(" ");
                }
                sb.append("\n");
            }
        }
        System.out.print(sb);
    }
}