1.实心三角形

代码：

1 import java.util.Scanner; 2  3 public class Test { 4  5     public static void main(String[] args) { 6         int rows; 7         Scanner sc = new Scanner(System.in); 8         System.out.println("Please input rows:"); 9         rows = sc.nextInt();10         sc.close();11         for (int i = 1; i <= rows; i++) {
    //控制打印行数12             for (int j = 1; j <= rows - i; j++) {
    //控制每行打印空格数13                 System.out.print(" ");14             }15             for (int j = 1; j <= i * 2 - 1; j++) {
    //控制打印星号数16                 System.out.print("*");17             }18             System.out.println();//每打一行，换行19         }20     }21 22 }

2.空心三角形

代码：

1 import java.util.Scanner; 2  3 public class Test { 4     public static void main(String[] args) { 5         int rows; 6         Scanner sc = new Scanner(System.in); 7         System.out.println("Please input rows:"); 8         rows = sc.nextInt(); 9         sc.close();10         for (int i = 1; i <= rows; i++) {11             for (int j = 1; j <= rows - i; j++) {12                 System.out.print(" ");13             }14             for (int j = 1; j <= 2 * i - 1; j++) {15                 if (i == 1 || i == rows) { // 如果是第一行或最后一行，打印所有星号16                     System.out.print("*");17                 } else if (j == 1 || j == 2 * i - 1) { // 如果是每行的第一个或者最后一个，打印星号18                     System.out.print("*");19                 } else { // 其余打印空格20                     System.out.print(" ");21                 }22             }23             System.out.println();24         }25     }26 }

3.实心菱形

代码：

1 import java.util.Scanner; 2  3 public class Test { 4     public static void main(String[] args) { 5         int rows; 6         Scanner sc = new Scanner(System.in); 7         System.out.println("Please input odd rows:");// 只能是奇数行 8         rows = (sc.nextInt() + 1) / 2;// 上半部分行数 9         sc.close();10         for (int i = 1; i <= rows; i++) {11             for (int j = 1; j <= rows - i; j++) {12                 System.out.print(" ");13             }14             for (int j = 1; j <= 2 * i - 1; j++) {15                 System.out.print("*");16             }17             System.out.println();18         }19         for (int i = rows - 1; i >= 1; i--) { // 下半部分不可重复打印上半部分最后一行，i=rows-1)20             for (int j = 1; j <= rows - i; j++) {21                 System.out.print(" ");22             }23             for (int j = 1; j <= 2 * i - 1; j++) {24                 System.out.print("*");25             }26             System.out.println();27         }28     }29 }

4.空心菱形

代码：

1 import java.util.Scanner; 2  3 public class Test { 4     public static void main(String[] args) { 5         int rows; 6         Scanner sc = new Scanner(System.in); 7         System.out.println("Please input odd rows:");// 只能是奇数行 8         rows = (sc.nextInt() + 1) / 2;// 上半部分行数 9         sc.close();10         sc.close();11         for (int i = 1; i <= rows; i++) {12             for (int j = 1; j <= rows - i; j++) {13                 System.out.print(" ");14             }15             for (int j = 1; j <= 2 * i - 1; j++) {16                 if (i == 1) {17                     System.out.print("*");18                 } else if (j == 1 || j == 2 * i - 1) {19                     System.out.print("*");20                 } else {21                     System.out.print(" ");22                 }23             }24             System.out.println();25         }26         for (int i = rows - 1; i >= 1; i--) {
    // 此处只需i=rows-1即可27             for (int j = 1; j <= rows - i; j++) {28                 System.out.print(" ");29             }30             for (int j = 1; j <= 2 * i - 1; j++) {31                 if (i == 1) {32                     System.out.print("*");33                 } else if (j == 1 || j == 2 * i - 1) {34                     System.out.print("*");35                 } else {36                     System.out.print(" ");37                 }38             }39             System.out.println();40         }41     }42 }