Java LongMath log10(long x, RoundingMode mode)用法及代码示例

Guava LongMath类的方法log10(long x，RoundingMode模式)接受两个参数，并根据第二个参数指定的舍入模式计算第一个参数的以10为底的对数。

用法:

public static int log10(long x, RoundingMode mode)

参数：该方法有两个参数：

x是要查找的日志的long值。
mode是指定的舍入模式。

返回值：此方法返回x的以10为底的对数，并根据指定的舍入模式进行舍入。

异常：此方法引发以下参数：

IllegalArgumentException：如果x值为0或负值。
ArithmeticException：如果mode为RoundingMode.UNNECESSARY且x不是10的幂。

Enum RoundingMode

枚举常量	描述
CEILING	舍入模式向正无穷大舍入。
DOWN	舍入模式向零舍入。
FLOOR	舍入模式向负无穷大舍入。
HALF_DOWN	除非两个邻居等距，否则舍入模式将朝“nearest neighbor”舍入。
HALF_EVEN	舍入模式向“nearest neighbor”舍入，除非两个邻居都等距，在这种情况下，向偶数邻居舍入。
HALF_UP	除非两个邻居等距，否则舍入模式将朝“nearest neighbor”舍入。
UNNECESSARY	舍入模式可以断言所请求的操作具有准确的结果，因此不需要舍入。
UP	舍入模式从零舍入。

下面给出了一些示例，以更好地理解实现：

范例1：

// Java code to show implementation of 
// log10(long x, RoundingMode mode) 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 a1 = 10000; 
  
        // Using log10(long x, RoundingMode mode) 
        // method of Guava's LongMath class 
        // The RoundingMode HALF_EVEN rounds towards 
        // the "nearest neighbor" unless both neighbors 
        // are equidistant, in which case, round towards 
        // the even neighbor. 
        System.out.println( 
            LongMath.log10( 
                a1, 
                RoundingMode.HALF_EVEN)); 
  
        long a2 = 15; 
  
        // Using log10(long x, RoundingMode mode) 
        // method of Guava's LongMath class 
        // The RoundingMode HALF_DOWN rounds towards 
        // "nearest neighbor" unless both neighbors 
        // are equidistant, in which case round down. 
        System.out.println( 
            LongMath.log10(a2, 
                           RoundingMode.HALF_DOWN)); 
    } 
}

输出：

4
1

范例2：

// Java code to show implementation of 
// log10(long x, RoundingMode mode) method 
// of Guava's LongMath class 
  
import java.math.RoundingMode; 
import com.google.common.math.LongMath; 
  
class GFG { 
  
    static int findlog10(long x, RoundingMode mode) 
    { 
        try { 
            // Using log10(long x, RoundingMode mode) 
            // method of Guava's LongMath class 
            // The RoundingMode HALF_EVEN rounds towards 
            // the "nearest neighbor" unless both neighbors 
            // are equidistant, in which case, round towards 
            // the even neighbor. 
            // This should throw "IllegalArgumentException" 
            // as x <= 0 
            int ans = LongMath.log10(x, mode); 
  
            // Return the answer 
            return ans; 
        } 
        catch (Exception e) { 
            System.out.println(e); 
            return -1; 
        } 
    } 
  
    // Driver code 
    public static void main(String args[]) 
    { 
        long x = -122; 
  
        try { 
  
            // Function calling 
            findlog10(x, RoundingMode.HALF_EVEN); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
}

输出：

java.lang.IllegalArgumentException:x (-122) must be > 0

参考： https://google.github.io/guava/releases/20.0/api/docs/com/google/common/math/LongMath.html#log10-long-java.math.RoundingMode-

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注：本文由纯净天空筛选整理自Sahil_Bansall大神的英文原创作品 Java Guava | LongMath log10(long x, RoundingMode mode) method with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。