Guava – LongMath.pow方法与实例

Guava的LongMath类的方法pow(long b, int k)返回b的第k次方。即使结果溢出，它也将等于BigInteger.valueOf(b).pow(k).longValue()。这个实现在O(log k)时间内运行。

语法:

public static long pow(long b, int k)

参数: 该方法接受两个参数，b和k。参数b被称为base，它被提高到k次方.

返回值： 这个方法返回b的k-th次方。

异常: 如果k是负数，这个方法会抛出IllegalArgumentException。

示例1:

// Java code to show implementation of// pow(long b, 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[])    {        long b1 = 4;        int k1 = 5;          long ans1 = LongMath.pow(b1, k1);          System.out.println(b1 + " to the " + k1                           + "th power is: "                           + ans1);          long b2 = 12;        int k2 = 3;          long ans2 = LongMath.pow(b2, k2);          System.out.println(b2 + " to the " + k2                           + "rd power is: "                           + ans2);    }}

输出:

4 to the 5th power is: 102412 to the 3rd power is: 1728

示例2:

// Java code to show implementation of// pow(long b, int k) method of Guava's// LongMath class  import java.math.RoundingMode;import com.google.common.math.LongMath;  class GFG {      static long findPow(long b, int k)    {        try {            // Using pow(long b, int k)            // method of Guava's LongMath class            // This should throw "IllegalArgumentException"            // as k < 0            long ans = LongMath.pow(b, k);              // Return the answer            return ans;        }        catch (Exception e) {            System.out.println(e);            return -1;        }    }      // Driver code    public static void main(String args[])    {        long b = 4;        int k = -5;          try {            // Using pow(long b, int k)            // method of Guava's LongMath class            // This should throw "IllegalArgumentException"            // as k < 0            LongMath.pow(b, k);        }        catch (Exception e) {            System.out.println(e);        }    }}

输出:

java.lang.IllegalArgumentException: exponent (-5) must be >= 0

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