Calculate poisson - Java Algorithm

Java examples for Algorithm:Statistics

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Description

Calculate poisson

Demo Code

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        double lambda = scan.nextDouble();
        int k = scan.nextInt();
        scan.close();// w w w  .j  av a  2s.  c o  m
        
        System.out.println(poisson(k, lambda));
    }
    
    private static double poisson(int k, double lambda) {
        return (Math.pow(lambda, k) * Math.pow(Math.E, -1 * lambda)) / factorial(k);
    }
    
    private static Long factorial (int n) {
        if (n < 0) {
            return null;
        }
        long result = 1;
        while (n > 0) {
            result *= n--;
        }
        return result;
    }
}

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