Finding Factorial using the BigInteger in JAVA

Up to Schooling we may only find factorial up to 25 but in real engineering we may have to deal with the largest numbers where the usual datatypes may not work. In Java , BigInteger is the pre-defined class we use in order to deal with those numbers.

Here in our example, using BigInteger we are finding factorial for larger Numbers.

import java.lang.*;
import java.util.Scanner;
import java.math.BigInteger;

public class HelloWorld {
    @ SuppressWarnings ("deprication")
    /*  The above line suppress the deprication warnings */
    public static void main(String[] args) {
    try{
        Scanner sc=new Scanner(System.in);
        int tests=Integer.parseInt(sc.next());
        BigInteger num,sum;
        String res;
        while(tests--!=0)
        {
        sum=new BigInteger("1");
        num=new BigInteger(sc.next());
        while(num.compareTo(new BigInteger("0"))!=0){
        sum=sum.multiply(num);
        num=num.subtract(new BigInteger("1"));
        }
        res+=sum+"\n";
        }
        System.out.println(res);
    }
    catch(Exception e){ System.out.println(e.getMessage()); }
    }
}

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Converting Numbers to Different Numerical Systems in JAVA

You may have to change the numbers from one format to other format, as like from decimal to hexagon . Here i have tried the different approach where you can convert from one numerical system to other numerical system using the digits in that numerical system.

For Example , if i want to convert the 10 from decimal to hexagon. I will provide the input in the following format along with the number of Test Cases.
1
# input1: 10 0123456789 0123456789abcdef
# output: a

Here is the logic for that written in JAVA language.

import java.lang.*;
import java.util.*;

public class Numbers{
    @ SuppressWarnings ("deprication")
    public static void main(String[] args)
    {   String result="";
        Scanner sc=new Scanner(System.in);
        int i=0,tests=Integer.parseInt(sc.next());
        while(i++<tests){
        String numbr=sc.next();
        String source_pattern=sc.next();
        String target_pattern=sc.next();
        Number_System source=new Number_System(source_pattern);
        Number_System target=new Number_System(target_pattern);
        result=result+"Case #"+i+": "+target.genValue(source.genDeciValue(numbr))+"\n";
            }
        System.out.print(result);
    }
}

class Number_System{
    int len=0;
    String pattern;
    public Number_System(String seq){
    len=seq.length();
    pattern=seq; }
    
    public int genDeciValue(String x){
        int i=0,v,str_len=x.length();
        Double value=new Double(0.0);
        while(i<str_len){
            v=pattern.indexOf(x.charAt(str_len-i-1));
            value=v*Math.pow(len,i)+value;
            i++;
        }
        return value.intValue();
    }
    
    public String genValue(int x){
        String res="";
        while(x!=0)
        {
            if(x<len){ res=pattern.charAt(x)+""+res; break; }
            res=pattern.charAt(x%len)+""+res;
            x=x/len;
        }
        return res;
    }
}

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Validating IPAddress in Java

This is the part of the java Regular Expressions, Validating,searching the data using the matches function This is mostly used in analyzing the data. To know further about it read about JAVA Regex  

import java.io.*;

public class ValidIP{

     public static void main(String []args){
       String IP="000.12.12.034";
       String pat="(([01]?(\\d)?(\\d))|([2]?([012345])?([012345])))";
       String pattern=pat+"."+pat+"."+pat+"."+pat;
       System.out.println(IP.matches(pattern));
     }
}

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