Java Big Data factorial (2)

Because the factorial result of a large number is relatively large, long integers cannot be stored. To achieve this function, multiply by BITs and store the result without bits separately, the final output, but the operation speed is a little slow. The calculation is 2000! It takes a long time, huh, huh. The idea is as follows:

24x5=    24 x   5 ------    20   10 ------   120

The Code is as follows:

import java.util.List;import java.util.ArrayList;class BigFactorial{public static void main(String args[]){BigFactorial bigFactorial = new BigFactorial();if(args.length >= 1){List<Integer> resultList = bigFactorial.computeFactorial(Integer.parseInt(args[0]));System.out.print("" + Integer.parseInt(args[0]) + "! = ");for( int i = 0; i < resultList.size(); i++){if( i == 0 && resultList.get(0) == 0){}else{System.out.print(""  + resultList.get(i));}}}}public List<Integer> computeFactorial(int paramNumber){List<Integer> localResult = new ArrayList<Integer>();if(paramNumber == 4){localResult.add(4);localResult.add(0, 2);return localResult;}else{List<Integer> multiplier = convertNumber(paramNumber);List<Integer> multiplicand = computeFactorial(paramNumber - 1);for(int i = multiplier.size() - 1; i >= 0; i--){for(int j = multiplicand.size() - 1; j >= 0; j--){int temp = 0;int result = multiplier.get(i) * multiplicand.get(j);if(result > 10){temp = result%10;result = result/10;}else{if(result == 10){result = 1;temp = 0;}else{temp = result;result = 0;}}if(localResult.size() == 0){localResult.add(temp);if(result != 0){localResult.add(0, result);}}else{int multiplierLength = multiplier.size() - 1 - i ;int multiplicandLength = multiplicand.size() - 1 - j;int insertNumber;int numberPast;if(multiplierLength == 0 || multiplicandLength == 0){numberPast = Math.max(multiplierLength, multiplicandLength);}else{numberPast = (multiplierLength + multiplicandLength);}insertNumber = localResult.size() - numberPast - 1;if(insertNumber == 0){int localParam1 = localResult.get(insertNumber) + temp;if(localParam1 >= 10){result = result + 1;localParam1 = localParam1%10;}localResult.set(insertNumber, localParam1);if(result != 0){localResult.add(0, result);}}else if(insertNumber == -1){localResult.add(0, temp);localResult.add(0, result);}else if(insertNumber == -2){localResult.add(0, 0);localResult.add(0, 0);localResult.add(0, temp);localResult.add(0, result);} else{int localParam2 = localResult.get(insertNumber) + temp;if(localParam2 >= 10){result++;localParam2 = localParam2%10;}localResult.set(insertNumber, localParam2);if(insertNumber == 0){localResult.add(0, result);}else{localResult.set(insertNumber - 1, (localResult.get(insertNumber - 1) + result));}}for( int r = localResult.size() - 1; r >= 0; r--){if(r == 0 && localResult.get(0) == 0){localResult.remove(0);}if(localResult.get(r) >= 10){int temp1 = localResult.get(r)%10;int result1 = localResult.get(r)/10;if(r == 0){localResult.set(0, temp1);localResult.add(0, 1);}else{localResult.set(r, temp1);localResult.set(r - 1, localResult.get(r - 1) + result1);}}}}}}return localResult;}}private List<Integer> convertNumber(int paramNumber){int remainder = paramNumber%10;int dValue = (paramNumber - remainder)/10;List<Integer> convertedNumber = new ArrayList<Integer>();convertedNumber.add(remainder);paramNumber = dValue;while(dValue != 0){if(dValue == 10){remainder = 0;dValue = 1;}else{remainder = paramNumber%10;convertedNumber.add(0, remainder);dValue = (paramNumber - remainder)/10;paramNumber = dValue;}}return convertedNumber;}}