3 ways in Java to print the Arithmetic Progression(AP) series

Java program to print the Arithmetic Progression or AP series:

In this post, we will learn how to print the Arithmetic Progression series in Java. An arithmetic progression series starts with a start item and calculates other items based on its position and another value called ‘common difference’.

For example, if the first item is a and the common difference is d, then the nth item in the arithmetic progression is a + (n - 1)*d. We can also get the next value if we add the common difference with the current value.

In this post, we will take the values of a, d, and n as inputs from the user. This program will print the first n values of the arithmetic progression starting from a.

We will learn different ways to solve this problem. Let’s check one by one:

Method 1: By using a for loop:

Let’s try to print this series by using a for loop. Below is the complete program:

import java.util.Scanner;

class Example1 {
    static void printAP(int a, int d, int n) {
        for (int i = 1; i <= n; i++) {
            System.out.print(a + (i - 1) * d + " ");
        }
    }

    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            int a, d, n;
            System.out.println("Enter the values of a, d and n: ");
            a = sc.nextInt();
            d = sc.nextInt();
            n = sc.nextInt();

            printAP(a, d, n);
        }
    }
}

It will print outputs as below:

Enter the values of a, d and n :
1
2
5
1 3 5 7 9

Download it on Github

Here,

• We are reading the values of a, d, and n from the user and assigning the values to the variables a, d, and n.
• The printAP() method is used to print the Arithmetic progression. This method uses a for loop that runs from i = 1 to i = n. For each value of i, it calculates and prints the current value of the Arithmetic progression series by using the formula we have discussed above.

Method 2: Without using the formula:

We can avoid using the formula to calculate each number of the AP series. Instead of that, we can add the value of d to the previous value of the series to get the current value. The following program shows how to write it programmatically:

import java.util.Scanner;

class Example2 {
    static void printAP(int a, int d, int n) {
        int currentValue = a;
        for (int i = 1; i <= n; i++) {
            System.out.print(currentValue + " ");
            currentValue += d;
        }
    }

    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            int a, d, n;
            System.out.println("Enter the values of a, d and n: ");
            a = sc.nextInt();
            d = sc.nextInt();
            n = sc.nextInt();

            printAP(a, d, n);
        }
    }
}

Download it on Github

Here,

• The printAP method initialized one variable currentValue with the value a.
• In the loop, it prints the value of currentValue and adds d to update its value as the next number of the series.

If you run this program, it will print similar outputs.

Method 3: By using a recursive method:

We can also solve it recursively. A recursive method calls itself again and again until an endpoint is reached. The below program shows how to write the program recursively:

import java.util.Scanner;

class Example3 {
    static void printAP(int d, int n, int current) {
        System.out.print(current + " ");

        if (n == 0)
            return;

        printAP(d, n - 1, current + d);
    }

    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            int a, d, n;

            System.out.println("Enter the values of a, d and n: ");
            a = sc.nextInt();
            d = sc.nextInt();
            n = sc.nextInt();

            printAP(d, n - 1, a);
        }

    }
}

Download it on Github

• The printAP() method is a recursive method. It calls itself again and again until the value of n is equal to 0.
• The variable current is the current value that we want to print. This value is incremented by d on each recursive call, i.e. it is changed to the next value.

If you run this program, it will print similar output as the above program.

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