Java对数

 1 public static double log(double a) {
 2         return StrictMath.log(a); // default impl. delegates to StrictMath
 3     }
 4 
 5     /**
 6      * Returns the base 10 logarithm of a value.返回10为底的对数
 7      * 
 8      ***Special cases特别注意:
 9      *
10      * 1.If the argument is NaN or less than zero, then the result is NaN.非数或小于0返回NAN
11      * 2.If the argument is positive infinity, then the result is positive infinity. 正无穷，返回正无穷
12      * 3.If the argument is positive zero or negative zero, then the result is negative infinity. 参数是正负0，返回负无穷
13      * 4. If the argument is equal to 10 ^n for integer n, then the result is n. 
14      * 
15      */

 1 public static double log10(double a) {
 2         return StrictMath.log10(a); // default impl. delegates to StrictMath
 3     }
 4 
 5 /** Returns the correctly rounded positive square root of a
 6      * value.
 7      * Special cases:
 8      * If the argument is NaN or less than zero, then the result is NaN.
 9      * If the argument is positive infinity, then the result is positive infinity.
10      * If the argument is positive zero or negative zero, then the
11      * result is the same as the argument.
12      * Otherwise, the result is the value closest to
13      * the true mathematical square root of the argument value.
14      * @return  the positive square root of .
15      *If the argument is NaN or less than zero, the result is NaN.
16      */
17 *翻译：
18 ＊特殊情况：
19 
20 *如果参数是NA或小于零，则结果是楠。
21 
22 *如果参数是正无穷大，则结果是正无穷大。
23 
24 *如果参数为正零或负零点，则
25 
26 *结果与论点相同。
27 
28 *否则，结果是最接近的值。
29 
30 *参数值的真正数学平方根。
31 
32 *@返回正平方根。
33 
34 *如果参数是NA或小于零，则结果是楠。
35 
36 */

1 public class Logarithm {
2     public int log(double value, int base){
3         return  (int)(Math.log(value)/Math.log(base));//换成了底数e
4     }
5 }