# next perm

```java
import java.util.Arrays;

public class next_permuation {
    public static void main(String[] args) {
        int[] nums = {1, 2, 3}; // Default test case

        nextPermutation(nums);

        System.out.println("Next permutation is: " + Arrays.toString(nums));
    }

    public static void nextPermutation(int[] nums) {
        int n = nums.length;

        int i=n-2;

        while(i>=0 && nums[i]>=nums[i+1])
        {
            i--;
        }
        if(i>=0)
        {
            int j= n-1;

            while(nums[i]>=nums[j])
            {
               j--;
            }
            swap(nums,i,j);
        }
        reverse(nums, i+1, n-1);
    }

    public static void swap(int[] nums, int i, int j) {
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }

    public static void reverse(int[] nums, int start, int end) {
        while (start < end) {
            swap(nums, start, end);
            start++;
            end--;
        }
    }
}
```