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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: Menu Driven Program to Display Triangle Number Patterns

10. Write a menu driven program that prompts the user to select one of the four triangle patterns (a, b, c or d). The program then accepts number of rows and prints the selected pattern as shown below:

Enter the size: 8

(a)
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
1 2 3 4 5 6
1 2 3 4 5 6 7
1 2 3 4 5 6 7 8
(b)
1 2 3 4 5 6 7 8
   1 2 3 4 5 6 7
      1 2 3 4 5 6
         1 2 3 4 5
            1 2 3 4
               1 2 3
                  1 2
                     1
(c)
                     1
                  1 2
               1 2 3
            1 2 3 4
         1 2 3 4 5
      1 2 3 4 5 6
   1 2 3 4 5 6 7
1 2 3 4 5 6 7 8
(d)
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7
1 2 3 4 5 6
1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

Java Program : Menu Driven Program to Display Triangle Number Patterns

Java 
import java.util.Scanner;


 


public class TriangleNumPatterns


{


    public static void main(String args[]) {


        Scanner in = new Scanner(System.in);


        System.out.println("Type a for Pattern a");


        System.out.println("Type b for Pattern b");


        System.out.println("Type c for Pattern c");


        System.out.println("Type d for Pattern d");


       


        System.out.print("Enter your choice: ");


        char ch = in.next().charAt(0);


       


        System.out.print("Enter the number of terms: ");


        int n = in.nextInt();


       


        switch (ch) {


            case 'a':


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


                    for (int j = 1; j <= i; j++)


                        System.out.print(j);


                    System.out.println();


                }


                break;


           


            case 'b':


                for (int i = n; i >= 1; i--)    {  


                    for (int j = i; j < n; j++)


                        System.out.print(" ");   


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


                        System.out.print(k);   


                    System.out.println();


                }


                break;


           


            case 'c':


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


                    for (int j = i; j < n; j++)


                        System.out.print(" ");


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


                        System.out.print(k);


                   


                    System.out.println();


                }


                break;


                


            case 'd':


                for (int i = n; i >= 1; i--) {


                    for (int j = 1; j <= i; j++)


                        System.out.print(j);


                    System.out.println();


                }


                break;


            default:


                System.out.println("Incorrect choice");


                break;


        }


    }


}

Output

Sample Output 1 : 
Type a for Pattern a
Type b for Pattern b
Type c for Pattern c
Type d for Pattern d
Enter your choice: a
Enter the number of terms: 8
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
1 2 3 4 5 6
1 2 3 4 5 6 7
1 2 3 4 5 6 7 8

Sample Output 2 : 
Type a for Pattern a
Type b for Pattern b
Type c for Pattern c
Type d for Pattern d
Enter your choice: b
Enter the number of terms: 8
 1 2 3 4 5 6 7 8
   1 2 3 4 5 6 7 
      1 2 3 4 5 6 
         1 2 3 4 5 
            1 2 3 4 
               1 2 3 
                  1 2 
                     1 

Sample Output 3 : 
Type a for Pattern a
Type b for Pattern b
Type c for Pattern c
Type d for Pattern d
Enter your choice: c
Enter the number of terms: 8
                     1
                  1 2
               1 2 3
            1 2 3 4 
         1 2 3 4 5 
      1 2 3 4 5 6
   1 2 3 4 5 6 7
1 2 3 4 5 6 7 8 

Sample Output 4 : 
Type a for Pattern a
Type b for Pattern b
Type c for Pattern c
Type d for Pattern d
Enter your choice: d
Enter the number of terms: 8
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7
1 2 3 4 5 6
1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

📝 Explanation

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