# Find the Sum of N Natural Numbers in Java ## Find the Sum of N Natural Numbers in Java

Given an integer input “num” the objective is to sum up all the numbers that lay in the interval [0,num]. To do so we’ll write a code to Find the Sum of N Natural Numbers in Java.

```Example
Input : 6
Output : 21
Explanation : 0 + 1 + 2 + 3 + 4 + 5 + 6 = 21.
```

### Find the Sum of N Natural Numbers in Java

Given an integer num input as the upper limit, the objective is to sum up all the numbers that lay in the interval starting from 0 to the integer input “num”. Here are some of the methods to sum up all the numbers in a given interval

• Method 1: Using for Loop
• Method 2: Using Formula
• Method 3: Using Recursion

We’ll discuss the above mentioned methods in detail in the sections below.

### Method 1: Using for Loop

In this method we’ll use for loop to iterate through the numbers in a range of [0,num].

### Working

For an integer input “num” we do the following

• initialize the required variables within the class.
• Run a for loop from 0 to num+1 meanwhile appending all the numbers to sum variable.
• Print the sum variable.

Let’s implement the logic in Java Language.

### Java Code

```public class Main
{
public static void main (String[]args)
{

int n = 10;
int sum = 0;

for (int i = 1; i <= n; i++)
sum += i;
System.out.println (sum);
}
}
```

```55
```

### Method 2: Using the Formula

In this method we’ll use a formula to find the sum of N integers in a series from sequence and series. The formula is mentioned below.

### Working

For an integer input we do the following operations

• Initialize the following variables.
• Implement the formula as sum = num * ( num + 1 ) / 2.
• Print the sum variable.

Let’s implement the above logic in Java language.

### Java Code

```public class Main
{
public static void main (String[]args)
{

int n = 10;

System.out.println ( n*(n+1)/2);
}
}
```

```55
```

### Method 3: Using Recursion

In this method we’ll use the concept of recursion to find the sum of all the number that lay from 0 to num. To know more about recursion, check out Recursion in Java

### Working

For a given integer input as “num” we perform the following steps

• Initialize the required variables.
• Define a recursive function with base case as num == 0.
• Set recursive step call as num + recursum(num-1).
• Call the recursive function and print the value returned by the function.

Let’s implement the above logic in Java Language.

### Java Code

```public class Main
{
public static void main (String[]args)
{

int n = 10;
int sum = getSum (n);

System.out.println (sum);
}

static int getSum (int n)
{
if (n == 0)
return n;

return n + getSum (n - 1);
}
}
```

```55
```

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