Java 倒三角

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
      Scanner scanner = new Scanner(System.in);
        System.out.print("请输入行数：");
        int row = scanner.nextInt();
        if (row >= 3 && row <= 21) {
            for (int i = 0; i < row; i++) {
                for (int j = 0; j < i; j++) {
                    System.out.print("");
                }
                for (int j = 0; j < 2 * (row - i) - 1; j++) {
                    System.out.print("*");
                }
                System.out.println();
            }
        } else {
            System.out.println("非法行数");
        }
    }
}

学习用