打印镜像下星三角形图案的Java程序

在本文中，我们将学习如何在Java打印镜像下星三角形图案。

插图：

Input: number = 7
Output:
* * * * * * * 
 * * * * * * 
  * * * * * 
   * * * * 
    * * * 
     * * 
      * 
      * 
     * * 
    * * * 
   * * * * 
  * * * * * 
 * * * * * * 
* * * * * * * 

方法：我们可以使用循环打印镜面下星三角形图案，所以

1. 使用 for 循环
2. 使用while循环
3. 使用 do-while 循环

方法一：使用for循环

例子

Java

// Java program to print Mirror Lower Star Triangle Pattern
// Using For loop
import java.io.*;
  
// Main class
class GFG {
  
    // Method
    // Main driver method
    public static void main(String[] args)
    {
        // Declare and initialize variable to
        // Size of the triangle
        int number = 7;
  
        // Declaring two variables for rows and columns
        int m, n;
  
        // Outer loop 1
        // Prints the first half triangle
        for (m = 1; m <= number; m++) {
  
            // Inner loop 1
            for (n = 1; n < m; n++) {
                // Print whitespace
                System.out.print(" ");
            }
  
            // Inner loop 2
            for (n = m; n <= number; n++) {
                // Print star
                System.out.print("*"
                                 + " ");
            }
  
            // Ending line after each row
            System.out.println();
        }
  
        // Outer loop 2
        // prints the second half triangle
        for (m = number - 1; m >= 0; m--) {
  
            // Inner loop 1
            for (n = 0; n < m; n++) {
                // Print whitespace
                System.out.print(" ");
            }
  
            // Inner loop 2
            for (n = m; n <= number - 1; n++) {
                // Print star
                System.out.print("*"
                                 + " ");
            }
  
            // Ending line after each row
            System.out.println();
        }
    }
}

输出

* * * * * * * 
 * * * * * * 
  * * * * * 
   * * * * 
    * * * 
     * * 
      * 
      * 
     * * 
    * * * 
   * * * * 
  * * * * * 
 * * * * * * 
* * * * * * * 

方法二：使用While循环

例子

Java

// Java program to Print Mirror Lower Star Triangle Pattern
// using While loop
import java.io.*;
  
// Main Class
class GFG {
  
    // Main driver method
    public static void main(String[] args)
    {
        // Declare and initialize variable to
        // Size of the triangle
        int number = 7;
  
        int m = number;
        int n;
  
        // Outer loop 1
        // prints the first half triangle
  
        // ill condition holds true
        while (m > 0) {
            n = 0;
  
            // Inner loop 1
            // prints space until n++ < number - m is false
            while (n++ < number - m) {
                // print whitespace
                System.out.print(" ");
            }
  
            n = 0;
  
            // Inner loop 2
            // Prints star until n++ < (m * 2) - 1 is false
            while (n++ < (m * 2) - 1) {
                // Print star
                System.out.print("*");
            }
  
            // Ending line after each row
            System.out.println();
  
            // Decrementing by one
            m--;
        }
  
        m = 1;
  
        // Outer loop 2
        // prints the second half triangle
        while (m <= number) {
            n = 0;
  
            // Inner loop 1
            // prints space until n++ < number - m is false
            while (n++ < number - m) {
                // Print whitespace
                System.out.print(" ");
            }
  
            n = 0;
  
            // Inner loop 2
            // Prints star until n++ < (m * 2) - 1 is false
            while (n++ < (m * 2) - 1) {
                // print star
                System.out.print("*");
            }
  
            // Ending line after each row
            System.out.println();
  
            m++;
        }
    }
}

输出

*************
 ***********
  *********
   *******
    *****
     ***
      *
      *
     ***
    *****
   *******
  *********
 ***********
*************

输出：

方法 3：使用 do-while 循环

执行：

例子

Java

// Java program to print Mirror Lower Star Triangle Pattern
// using Do-while loop
import java.io.*;
  
// Main class
class GFG {
  
    // Main driver method
    public static void main(String[] args)
    {
        // Declare variable with the
        // Size of the triangle
        int number = 7;
  
        int m = number;
        int n;
  
        // Outer loop 1
        // prints the first half triangle
        do {
            n = 0;
  
            // Inner loop 1
            // prints space until n++ < number - m is false
            do {
                // Print whitespaces
                System.out.print(" ");
  
            } while (n++ < number - m);
  
            n = 0;
  
            // Inner loop 2
            // prints star until n++ < m * 2 - 2 is false
            do {
                // Print star
                System.out.print("*");
            }
  
            while (n++ < m * 2 - 2);
  
            System.out.println("");
  
        }
  
        // Condition check for do-while
        while (--m > 0);
  
        m = 1;
  
        // Outer loop 2
        // prints the second half triangle
        do {
            n = 0;
  
            // Inner loop 1
            // prints space until n++ < (number - m) is
            // false
            do {
                // Print whitespace
                System.out.print(" ");
  
            } while (n++ < (number - m));
  
            n = 0;
  
            // Inner loop 2
            // prints star until n++ < (m * 2) - 2 is false
            do {
                // Print star
                System.out.print("*");
            }
  
            while (n++ < (m * 2) - 2);
  
            System.out.println("");
  
        }
  
        // Condition check for do-while
        while (++m <= number);
    }
}

输出

*************
  ***********
   *********
    *******
     *****
      ***
       *
       *
      ***
     *****
    *******
   *********
  ***********
 *************