Guava BigIntegerMath类的方法log2(BigInteger x,RoundingMode模式)返回x的以2为底的对数,并根据指定的舍入模式进行四舍五入。
用法:
public static int log2(BigInteger x, RoundingMode mode)
参数:此方法采用以下参数:
- x:要查找其日志的BigInteger号。
- mode:用于计算2的对数的舍入模式。
返回值:此方法返回x的以2为底的对数,并根据指定的舍入模式进行舍入。
异常:此方法引发以下异常:
- IllegalArgumentException:如果x <= 0。
- ArithmeticException:如果mode为RoundingMode.UNNECESSARY且x不是2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。 |
以下示例说明了BigIntegerMath.log2()方法:
范例1:
// Java code to show implementation of
// log2(BigInteger x, RoundingMode mode) method
// of Guava's BigIntegerMath class
import java.math.*;
import com.google.common.math.BigIntegerMath;
class GFG {
// Driver code
public static void main(String args[])
{
BigInteger a1 = BigInteger.valueOf(1024);
// Using log2(BigInteger x, RoundingMode mode)
// method of Guava's BigIntegerMath 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("Log base 2 of " + a1
+ " with rounding mode HALF_EVEN = "
+ BigIntegerMath
.log2(a1,
RoundingMode.HALF_EVEN));
BigInteger a2 = BigInteger.valueOf(15);
// Using log2(BigInteger x, RoundingMode mode)
// method of Guava's BigIntegerMath class
// The RoundingMode HALF_DOWN rounds towards
// "nearest neighbor" unless both neighbors
// are equidistant, in which case round down.
System.out.println("Log base 2 of " + a2
+ " with rounding mode HALF_DOWN = "
+ BigIntegerMath
.log10(a2,
RoundingMode.HALF_DOWN));
}
}
输出:
Log base 2 of 1024 with rounding mode HALF_EVEN = 10 Log base 2 of 15 with rounding mode HALF_DOWN = 1
范例2:显示IllegalArgumentException
// Java code to show implementation of
// log2(BigInteger x, RoundingMode mode) method
// of Guava's BigIntegerMath class
import java.math.*;
import com.google.common.math.BigIntegerMath;
class GFG {
// Driver code
public static void main(String args[])
{
try {
BigInteger a1 = BigInteger.valueOf(-5);
// Using log2(BigInteger x, RoundingMode mode)
// method of Guava's BigIntegerMath 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 a1 <= 0
System.out.println("Log base 2 of " + a1
+ " with rounding mode HALF_EVEN = "
+ BigIntegerMath
.log2(a1,
RoundingMode.HALF_EVEN));
}
catch (Exception e) {
System.out.println("Exception:" + e);
}
}
}
输出:
Exception:java.lang.IllegalArgumentException:x (-5) must be > 0
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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 BigIntegerMath log2() function | Guava | Java。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。