4． 案例4-1，打印不同的图形（正方形与菱形，使用抽象类）。

abstract class shape{
    abstract void fang();
    abstract void leng();
}
class run extends shape {
    public void fang() {
        int x = 4;
        for (int i = 0; i <= 4; i++) {
            for (int j = 0; j <= 4; j++) {
                System.out.print("*");
            }
            System.out.println();

        }
    }

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

            for (int j = 1; j <= 4 - i; j++) {
                System.out.print(" ");
            }

            for (int k = 1; k <= 2 * i - 1; k++) {
                System.out.print("*");
            }

            System.out.println();
        }

        for (int i = 3; i >= 1; i--) {
            for (int j = 1; j <= 4 - i; j++) {
                System.out.print(" ");
            }
            for (int k = 1; k <= 2 * i - 1; k++) {
                System.out.print("*");
            }

            System.out.println();
        }
    }
}

public class driver {//自定义的driver类

    public static void main(String[] args) {
        run r = new run();
        r.fang();
        r.leng();
    }
}