WAP to Factorial of Very Big Number

Source - Algoseekar (Developer)
https://github.com/algoseeker/Interview/blob/b8b1aac7b133beb94637e17deea578ae29948271/factorial/Decimal.java



import java.lang.String;
import java.lang.StringBuilder;
import java.io.Console;

public class Decimal{
protected String number;

public Decimal(String s){
int i;
for(i=0;iif(s.charAt(i)!='0')
break;
}
this.number = s.substring(i,s.length());
}
public void add(Decimal anum){
this.number = Decimal.add(this,anum);
}
public void multiply(Decimal anum){
number = Decimal.multiply(this, anum).getNum();
}

public static Decimal multiply(Decimal num, Decimal num2){
Decimal greater;
Decimal smaller;
if(num.size()>=num2.size()){
greater = num;
smaller = num2;
} else{
greater = num2;
smaller = num;
}
StringBuilder ans = new StringBuilder();
String s1 = greater.getNum();
String s2 = smaller.getNum();
Decimal b = new Decimal("0");

for(int i=smaller.size()-1;i>=0;i--){
if(s2.charAt(i)!='0'){
String s = Decimal.multiply(s1,s2.charAt(i)-'0');
Decimal temp = new Decimal(Decimal.padZeroes(s,(smaller.size()-i-1)));
b.add(temp);
}
}
return b;
}

public static String multiply(String s, int single_digit){
int carry=0;
StringBuilder ans = new StringBuilder();
for(int i=s.length()-1;i>=0;i--){
int n = s.charAt(i) - '0';
int result = n * single_digit + carry;
carry = result/10;
ans.append(result%10);
}
if(carry!=0){
ans.append(carry);
}
return ans.reverse().toString();
}

public static String padZeroes(String s, int nzeroes){
StringBuilder ans = new StringBuilder(s);
for(int i=0;ians.append('0');
return ans.toString();
}

public static String add(Decimal num, Decimal num2){
Decimal greater;
Decimal smaller;
if(num.size()>=num2.size()){
greater = num;
smaller = num2;
} else{
greater = num2;
smaller = num;
}
int carry = 0;
int i= greater.size()-1;
String s1 = greater.getNum();
String s2 = smaller.getNum();
StringBuilder ans = new StringBuilder();
for(int j=smaller.size()-1;j>=0;j--,i--){
int digit1 = s1.charAt(i) - '0';
int digit2 = s2.charAt(j) - '0';
int result = digit1 + digit2 + carry;
carry = result/10;
ans.append(result%10);
}

// Adding the carry over left after adding smaller number
while(i>=0){
int n = s1.charAt(i) - '0';
int result = n + carry;
ans.append(result%10);
carry = result/10;
i--;
}
if(carry>0){
ans.append(carry);
}
if(ans.length()==0)
ans.append('0');
ans.reverse();
return ans.toString();
}

public int size(){
return number.length();
}

public String getNum(){
return number;
}
public static void main(String[] args){
Console c = System.console();
String num1 = c.readLine("Enter first decimal:");
String num2 = c.readLine("Enter second decimal:");
Decimal b1 = new Decimal(num1);
Decimal b2 = new Decimal(num2);
System.out.println("Num1: " + b1.getNum());
System.out.println("Num2: " + b2.getNum());

Decimal b3 = Decimal.multiply(b1,b2);
System.out.println("Result: " + b3.getNum());
System.out.println("Size:" +b3.getNum().length());

}
}