Java番石榴 | IntMath log10(int x, RoundingMode mode) 方法与示例
Guava 的 IntMath 类的log10(int x, RoundingMode mode)方法接受两个参数,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 为底的对数值。
句法:
public static int log10(int x, RoundingMode mode)
参数:该方法有 2 个参数:
- x是要查找日志的 int 值。
- mode是指定的舍入模式。
返回值:此方法返回 x 的 Base-10 对数,根据指定的舍入方式进行舍入。
例外:此方法抛出以下参数:
- IllegalArgumentException:如果值 x 为 0 或负值。
- ArithmeticException:如果 mode 是 RoundingMode.UNNECESSARY 并且 x 不是 10 的幂。
枚举舍入模式
Enum Constant | Description |
---|---|
CEILING | Rounding mode to round towards positive infinity. |
DOWN | Rounding mode to round towards zero. |
FLOOR | Rounding mode to round towards negative infinity. |
HALF_DOWN | Rounding mode to round towards “nearest neighbor” unless both neighbors are equidistant, in which case round down. |
HALF_EVEN | Rounding mode to round towards the “nearest neighbor” unless both neighbors are equidistant, in which case, round towards the even neighbor. |
HALF_UP | Rounding mode to round towards “nearest neighbor” unless both neighbors are equidistant, in which case round up. |
UNNECESSARY | Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. |
UP | Rounding mode to round away from zero. |
下面给出了一些示例,以更好地理解实现:
示例 1:
// Java code to show implementation of
// log10(int x, RoundingMode mode) method
// of Guava's IntMath class
import java.math.RoundingMode;
import com.google.common.math.IntMath;
class GFG {
// Driver code
public static void main(String args[])
{
int a1 = 10000;
// Using log10(int x, RoundingMode mode)
// method of Guava's IntMath 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(
IntMath.log10(a1,
RoundingMode.HALF_EVEN));
int a2 = 15;
// Using log10(int x, RoundingMode mode)
// method of Guava's IntMath class
// The RoundingMode HALF_DOWN rounds towards
// "nearest neighbor" unless both neighbors
// are equidistant, in which case round down.
System.out.println(
IntMath.log10(a2,
RoundingMode.HALF_DOWN));
}
}
输出 :
4
1
示例 2:
// Java code to show implementation of
// log10(int x, RoundingMode mode) method
// of Guava's IntMath class
import java.math.RoundingMode;
import com.google.common.math.IntMath;
class GFG {
static int findlog10(int x, RoundingMode mode)
{
try {
// Using log10(int x, RoundingMode mode)
// method of Guava's IntMath 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 = IntMath.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[])
{
int x = -152;
try {
// Function calling
findlog10(x, RoundingMode.HALF_EVEN);
}
catch (Exception e) {
System.out.println(e);
}
}
}
输出 :
java.lang.IllegalArgumentException: x (-152) must be > 0
参考: https://google.github.io/guava/releases/20.0/api/docs/com/google/common/math/IntMath.html#log10-int-java.math.RoundingMode-