Java Guava LongMath pow(long b, int k)用法及代碼示例

Guava LongMath類的方法pow(long b，int k)將b返回到第k次冪。即使結果溢出，也將等於BigInteger.valueOf(b).pow(k).longValue()。此實現在O(log k)時間中運行。

用法:

public static long pow(long b, int k)

參數：該方法接受兩個參數b和k。參數b稱為基數，它升為k-th的冪。

返回值：此方法返回b的k-th冪。

異常：如果k為負，則此方法引發IllegalArgumentException。

範例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); 
    } 
}

輸出：

4 to the 5th power is:1024
12 to the 3rd power is:1728

範例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); 
        } 
    } 
}

輸出：

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

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

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注：本文由純淨天空篩選整理自Sahil_Bansall大神的英文原創作品 Java Guava | pow(long b, int k) of LongMath Class with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。