public class HelloWorld {

        public static void main(String[] args) {

         System.out.println("打印直角三角形");

                 for (int i = 1;i<4;i++) {

                         for (int j = 1;j<i;j++) {System.out.print(" ");

                  }

                  for (int j = 1;j<=4-i;j++) {

                          System.out.print("*");

                   }

                   System.out.println();

                   }

         }

}

这样吗？