Nested for Loops in Java

Chapter 10

Nested for Loops in Java

Class 10 - Logix Kips ICSE Computer Applications with BlueJ

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Java Program: Triangle or Inverted Triangle Pattern in Java

6. Write a program to generate a triangle or an inverted triangle till n terms based upon the user's choice of triangle to be displayed.

Example 1

Input:
Type 1 for a triangle and type 2 for an inverted triangle
1
Enter the number of terms
5

Output:

2 2

3 3 3

4 4 4 4

5 5 5 5 5

Example 2

Input:
Type 1 for a triangle and type 2 for an inverted triangle
2
Enter the number of terms
6

Output:

6 6 6 6 6 6

5 5 5 5 5

4 4 4 4

3 3 3

2 2

Program Title 1 : Value of sum After Nested Loops Execution in Java

Java

import java.util.Scanner;
 
public class NumberTriangle
{
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
 
        System.out.println("Type 1 for a triangle and type 2 for an inverted triangle");
        int choice = sc.nextInt();
 
        System.out.println("Enter the number of terms");
        int n = sc.nextInt();
 
        switch(choice)
        {
            case 1: // Normal Triangle
                for(int i = 1; i <= n; i++)
                {
                    for(int j = 1; j <= i; j++)
                    {
                        System.out.print(i + " ");
                    }
                    System.out.println();
                }
                break;
 
            case 2: // Inverted Triangle
                for(int i = n; i >= 1; i--)
                {
                    for(int j = 1; j <= i; j++)
                    {
                        System.out.print(i + " ");
                    }
                    System.out.println();
                }
                break;
 
            default:
                System.out.println("Invalid Choice");
        }
 
        sc.close();
    }
}

Output

Sample Output 1: 
Type 1 for a triangle and type 2 for an inverted triangle
1
Enter the number of terms
5
1 
2 2 
3 3 3 
4 4 4 4 
5 5 5 5 5 

Sample Output 2: 
Type 1 for a triangle and type 2 for an inverted triangle
2
Enter the number of terms
6
6 6 6 6 6 6 
5 5 5 5 5 
4 4 4 4 
3 3 3 
2 2 
1

📝 Explanation

✔ When user enters 1

Outer loop runs from 1 to n
Inner loop prints the number i, i times

Example (n = 5):

✔ When user enters 2

Outer loop runs from n to 1
Inner loop prints the number i, i times

Example (n = 6):