Example: Pascal's Triangle using While Loop in Java

// Pascal's Triangle using While Loop
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Initialize a Scanner for user input
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter the number of rows for Pascal's Triangle: ");
        int numRows = scanner.nextInt();
        scanner.close();

        // Step 2: Create a list to store all rows of the triangle
        List<List<Integer>> pascalTriangle = new ArrayList<>();

        // Step 3: Outer while loop to iterate through each row
        int currentRowNum = 0;
        while (currentRowNum < numRows) {
            // Create a list for the current row
            List<Integer> currentRow = new ArrayList<>();
            
            // Inner while loop to populate elements of the current row
            int elementIndex = 0;
            while (elementIndex <= currentRowNum) {
                // The first and last elements of each row are always 1
                if (elementIndex == 0 || elementIndex == currentRowNum) {
                    currentRow.add(1);
                } else {
                    // For other elements, sum the two numbers from the previous row
                    // specifically, the element at (elementIndex-1) and (elementIndex)
                    List<Integer> prevRow = pascalTriangle.get(currentRowNum - 1);
                    int sum = prevRow.get(elementIndex - 1) + prevRow.get(elementIndex);
                    currentRow.add(sum);
                }
                elementIndex++;
            }
            
            // Add the completed current row to the pascalTriangle list
            pascalTriangle.add(currentRow);
            
            currentRowNum++; // Move to the next row
        }

        // Step 4: Print the Pascal's Triangle
        int i = 0;
        while (i < pascalTriangle.size()) {
            List<Integer> rowToPrint = pascalTriangle.get(i);
            int j = 0;
            while (j < rowToPrint.size()) {
                System.out.print(rowToPrint.get(j) + " ");
                j++;
            }
            System.out.println(); // Move to the next line after printing a row
            i++;
        }
    }
}