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