Java calculates the sum of 1-N factorials

From , 3 Years ago, written in Java, viewed 53 times.

import java.math.BigInteger;  
  
public class Test02{  
      
    /** 
     * 计算从1到n个数的阶乘的总和 
     * @param s 
     * @return 
     */  
    public static BigInteger summation(int n){  
        BigInteger sum = new BigInteger("0");  
        if(n <= 1) return BigInteger.ONE;    //因0！= 1  所以 n <= 1 时返回 1  
        for(int i=1; i<=n; i++){           
            sum = sum.add(factorial(i));  
        }  
        return sum;  
    }  
    /** 
     * （递归）计算 n 的阶乘 
     * @param n 
     * @return sum 
     */  
    public static BigInteger factorial(int n){        
        if(n > 0){             
            return BigInteger.valueOf(n).multiply(factorial(n-1));  
        }else{      //因0！= 1   所以 n <= 1 时返回 1  
            return BigInteger.ONE;  
        }  
    }  
    public static void main(String[] args){  
        for(int i=1; i<=30; i++){  
            System.out.println(i + " 的阶乘 = " + factorial(i));  
        }  
        for(int i=1; i<=30; i++){  
            System.out.println("从1到" + i + "的阶乘的总和  = " + summation(i));  
        }                 
    }  
} 
 
 
//java/7035

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import java.math.BigInteger;  
  
public class Test02{  
      
    /** 
     * 计算从1到n个数的阶乘的总和 
     * @param s 
     * @return 
     */  
    public static BigInteger summation(int n){  
        BigInteger sum = new BigInteger("0");  
        if(n <= 1) return BigInteger.ONE;    //因0！= 1  所以 n <= 1 时返回 1  
        for(int i=1; i<=n; i++){           
            sum = sum.add(factorial(i));  
        }  
        return sum;  
    }  
    /** 
     * （递归）计算 n 的阶乘 
     * @param n 
     * @return sum 
     */  
    public static BigInteger factorial(int n){        
        if(n > 0){             
            return BigInteger.valueOf(n).multiply(factorial(n-1));  
        }else{      //因0！= 1   所以 n <= 1 时返回 1  
            return BigInteger.ONE;  
        }  
    }  
    public static void main(String[] args){  
        for(int i=1; i<=30; i++){  
            System.out.println(i + " 的阶乘 = " + factorial(i));  
        }  
        for(int i=1; i<=30; i++){  
            System.out.println("从1到" + i + "的阶乘的总和  = " + summation(i));  
        }                 
    }  
}

//java/7035

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Java calculates the sum of 1-N factorials

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