解题就干一件事：找j,k与i的关系(规律)

*/

public class PrintPyramid {

public static void main(String[] args) {

int n = 6;

printPyramid(n); //打印实心金字塔

System.out.println("------------------------------------------");

printReversedPyramid(n); //打印倒的实心金字塔

System.out.println("------------------------------------------");

printHollowPyramid(n); //打印空心金字塔

System.out.println("------------------------------------------");

printReversedHollowPyramid(n); //打印倒的空心金字塔

System.out.println("------------------------------------------");

printRhombus(n); //打印实心菱形

System.out.println("------------------------------------------");

printHollowRhombus(n); //打印空心菱形

}

/*

打印正的实心金字塔

*

***

*****

*******

/

private static void printPyramid(int n) {

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

for (int k = 1;k <= n - i;k++) {

System.out.print(" ");

}

for (int j = 1;j <= 2 * i - 1;j++) {

System.out.print("");

}

System.out.println();

}

}

/*

打印倒的实心金字塔

*******

*****

***

*

/

private static void printReversedPyramid(int n) {

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

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

System.out.print(" ");

}

/

先死后活法找规律

先死：

n = 4; 2 * n - 1

i 1 2 3 4

*个数 7 5 3 1

规律：7 + (i - 1) * (-2)

后活：

(2 * n - 1) + (i - 1) * (-2) = 2 * n - 2 * i + 1

/

for (int j = 1;j <= 2 * n - 2 * i + 1;j++) {

System.out.print("");

}

System.out.println();

}

}

/*

打印正的空心金字塔

*

* *

* *

*******

/

private static void printHollowPyramid(int n) {

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

if (i == 1) {

for (int k = 1;k <= n - 1;k++) {

System.out.print(" ");

}

System.out.println("");

} else if (i == n) {

for (int j = 1; j <= 2 * n - 1 ; j++) {

System.out.print("");

}

System.out.println();

} else {

for (int k = 1;k <= n - i;k++) {

System.out.print(" ");

}

System.out.print("");

for (int k = 1; k <= 2 * i - 3 ; k++) {

System.out.print(" ");

}

System.out.print("*");

System.out.println();

}

}

}

/*

打印倒的空心金字塔

*******

* *

* *

*

/

private static void printReversedHollowPyramid(int n) {

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

if (i == 1) {

for (int j = 1; j <= 2 * n - 1 ; j++) {

System.out.print("");

}

System.out.println();

} else if (i == n) {

for (int k = 1;k <= n - 1;k++) {

System.out.print(" ");

}

System.out.println("");

} else {

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

System.out.print(" ");

}

System.out.print("");

for (int k = 1; k <= 2 * n - 2 * i - 1 ; k++) {

System.out.print(" ");

}

System.out.print("*");

System.out.println();

}

}

}

/*

打印实心菱形

*

***

*****

*******

*****

***

*

/

private static void printRhombus(int n) {

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

for (int k = 1;k <= n - i;k++) {

System.out.print(" ");

}

for (int j = 1;j <= 2 * i - 1;j++) {

System.out.print("");

}

System.out.println();

}

printReversedPyramid(n);

}

/*

打印空心菱形

*

* *

* *

* *

* *

* *

*

/

private static void printHollowRhombus(int n) {

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

if (i == 1) {

for (int k = 1;k <= n - 1;k++) {

System.out.print(" ");

}

System.out.println("");

} else if (i == n) {

for (int j = 1; j <= 2 * n - 1 ; j++) {

System.out.print("");

}

System.out.println();

} else {

for (int k = 1;k <= n - i;k++) {

System.out.print(" ");

}

System.out.print("");

for (int k = 1; k <= 2 * i - 3 ; k++) {

System.out.print(" ");

}

System.out.print("*");

System.out.println();

}

}

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

if (i == 1) {

System.out.print("*");

for (int k = 1; k <= 2 * n - 3 ; k++) {

System.out.print(" ");

}

System.out.print("*");

System.out.println();

} else if (i == n) {

for (int k = 1;k <= n - 1;k++) {

System.out.print(" ");

}

System.out.println("*");

} else {

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

System.out.print(" ");

}

System.out.print("*");

for (int k = 1; k <= 2 * n - 2 * i - 1 ; k++) {

System.out.print(" ");

}

System.out.print("*");

System.out.println();

}

}

}