Guava LongMath类
LongMath 是用来对Long值进行数学运算。基本的独立数学函数根据涉及的主要数字类型分为IntMath、LongMath、DoubleMath和BigIntegerMath类。这些类具有平行结构,但每个类只支持相关的函数子集。
声明 : com.google.common.math.LongMath类的声明是 :
@GwtCompatible(emulated = true)
public final class LongMath
extends Object
下表显示了Guava的LongMath类提供的一些方法。
异常 :
- log2 : 如果x<=0,则出现IllegalArgumentException
- log10 : 如果x<=0,则出现IllegalArgumentException
- pow : 如果k<0,则出现IllegalArgumentException
- sqrt : 如果x<0,则出现IllegalArgumentException
- divide : 如果q==0,或者mode==UNNECESSARY,且a不是b的整数倍,则出现ArithmeticException
- mod : 如果m<=0,则出现算术异常
- gcd : 如果a<0或b<0,则出现IllegalArgumentException
- checkedAdd: 如果a + b在有符号长算术中溢出,则出现算术异常
- checkedSubtract : 如果a – b在有符号长算术中溢出,则出现算术异常
- checkedMultiply : checkedPow : 如果a * b在有符号长算术中溢出,则出现算术异常
- checkedPow : 如果b的k次方在有符号长算术中溢出,则出现算术异常
- factorial : 如果n<0,则出现IllegalArgumentException
- binomial : 如果n<0,k<0或k>n
Guava的LongMath类提供的一些其他方法是。
例子1 :
// Java code to show implementation of
// LongMath Class of Guava
import java.math.RoundingMode;
import com.google.common.math.LongMath;
class GFG {
// Driver code
public static void main(String args[])
{
// Creating an object of GFG class
GFG obj = new GFG();
// Function calling
obj.examples();
}
private void examples()
{
try {
// exception will be thrown as 80 is not
// completely divisible by 3
// thus rounding is required, and
// RoundingMode is set as UNNESSARY
System.out.println(LongMath.divide(80, 3, RoundingMode.UNNECESSARY));
}
catch (ArithmeticException ex) {
System.out.println("Error Message is : " + ex.getMessage());
}
}
}
输出:
Error Message is : mode was UNNECESSARY, but rounding was necessary
例子2 :
// Java code to show implementation of
// LongMath Class of Guava
import java.math.RoundingMode;
import com.google.common.math.LongMath;
class GFG {
// Driver code
public static void main(String args[])
{
// Creating an object of GFG class
GFG obj = new GFG();
// Function calling
obj.examples();
}
private void examples()
{
// As 120 is divisible by 4, so
// no exception is thrown
System.out.println(LongMath.divide(120, 4, RoundingMode.UNNECESSARY));
// To compute GCD of two integers
System.out.println("GCD is : " + LongMath.gcd(70, 14));
// To compute log to base 10
System.out.println("Log10 is : " + LongMath.log10(1000, RoundingMode.HALF_EVEN));
// To compute remainder
System.out.println("modulus is : " + LongMath.mod(125, 5));
// To compute factorial
System.out.println("factorial is : " + LongMath.factorial(7));
// To compute log to base 2
System.out.println("Log2 is : " + LongMath.log2(8, RoundingMode.HALF_EVEN));
// To compute square root
System.out.println("sqrt is : " + LongMath.sqrt(LongMath.pow(12, 2), RoundingMode.HALF_EVEN));
}
}
输出:
30
GCD is : 14
Log10 is : 3
modulus is : 0
factorial is : 5040
Log2 is : 3
sqrt is : 12
参考资料 :Google Guava