Guava – LongMath.binomial方法与实例

Guava的LongMath类的binomial(int n, int k)方法接受两个参数 n and k ，并计算二项式系数的值 。如果计算值超过长的最大值，则该方法返回Long.MAX_VALUE即长的最大值。

语法:

public static long binomial(int n, int k)

参数 : 该方法接受两个参数 n and k 并计算二项式系数的值 .

返回值 : 该方法返回 n 和 k 的二项式系数。

异常 : 如果 n 是负数，或 k 是负数，或 k 大于 n，则 binomial(int n, int k) 方法抛出 IllegalArgumentException。

以下例子说明了 LongMath 类的 binomial（）方法。

例子 1 :

// Java code to show implementation of
// binomial(int n, int k) method of Guava's
// LongMath class
import java.math.RoundingMode;
import com.google.common.math.LongMath;
  
class GFG {
  
    // Driver code
    public static void main(String args[])
    {
        int n = 4;
        int k = 3;
  
        // Using binomial(int n, int k) method of
        // Guava's LongMath class
        long ans = LongMath.binomial(n, k);
  
        System.out.println("Binomial Coefficient of "
                           + n + " and " + k
                           + " is : " + ans);
  
        int n1 = 20;
        int k1 = 4;
  
        // Using binomial(int n, int k) method of
        // Guava's LongMath class
        long ans1 = LongMath.binomial(n1, k1);
  
        System.out.println("Binomial Coefficient of "
                           + n1 + " and " + k1
                           + " is : " + ans1);
    }
}

输出:

Binomial Coefficient of 4 and 3 is : 4
Binomial Coefficient of 20 and 4 is : 4845

例子 2 :

// Java code to show implementation of
// binomial(int n, int k) method of Guava's
// LongMath class
  
import java.math.RoundingMode;
import com.google.common.math.LongMath;
  
class GFG {
  
    static long findBinomial(int n, int k)
    {
        try {
            // Using binomial(int n, int k)
            // method of Guava's LongMath class
            // This should throw "IllegalArgumentException"
            // as k < 0
            long ans = LongMath.binomial(n, k);
  
            // Return the answer
            return ans;
        }
        catch (Exception e) {
            System.out.println(e);
            return -1;
        }
    }
  
    // Driver code
    public static void main(String args[])
    {
        int n = 5;
        int k = 7;
  
        try {
            // Function calling
            findBinomial(n, k);
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出:

java.lang.IllegalArgumentException: k (7) > n (5)

参考资料 : https://google.github.io/guava/releases/20.0/api/docs/com/google/common/math/LongMath.html#binomial-int-int-