Iterative Constructs in Java

Chapter 9

Iterative Constructs in Java

Class 10 - Logix Kips ICSE Computer Applications with BlueJ

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Java Program: Product of Series using for, while and do-while Loops

13. Write three different programs using for, while, and do-while loops to find the product of series 3, 9, 12,... 30.

Program 1: Using for loop

Java Program: Product of Series using For Loop

Java

public class ProductForLoop {
    public static void main(String[] args) {
 
        long product = 1;
        int num = 3;
 
        for (int i = 1; num <= 30; i++) {
            product *= num;
 
            if (i % 2 == 1)
                num += 6;
            else
                num += 3;
        }
 
        System.out.println("Product of the series = " + product);
    }
}

Output

Sample Output
Product of the series = 248031360

Program 2: Using while loop

Java Program: Product of Series using while Loop

Java

public class ProductWhileLoop {
    public static void main(String[] args) {
 
        long product = 1;
        int num = 3;
        int count = 1;
 
        while (num <= 30) {
            product *= num;
 
            if (count % 2 == 1)
                num += 6;
            else
                num += 3;
 
            count++;
        }
 
        System.out.println("Product of the series = " + product);
    }
}

Output

Sample Output
Product of the series = 248031360

Program 3: Using do-while loop

Java Program: Product of Series using do-while Loop

Java

public class ProductDoWhileLoop {
    public static void main(String[] args) {
 
        long product = 1;
        int num = 3;
        int count = 1;
 
        do {
            product *= num;
 
            if (count % 2 == 1)
                num += 6;
            else
                num += 3;
 
            count++;
        } while (num <= 30);
 
        System.out.println("Product of the series = " + product);
    }
}

Output

Output
Product of the series = 248031360

📝 Explanation

Start with num = 3
Multiply each term with product
Increase number alternately by 6 and 3
Stop when value exceeds 30
long is used to avoid overflow