Guava 12-mathematical operations

Example

int logfloor = LONGMATH.LOG2 (n, floor), int mustnotoverflow = intmath.checkedmultiply (x, y); long quotient = Longmath.divid E (Knownmultipleofthree, 3, roundingmode.unnecessary); Fail fast on non-multiple of 3BigInteger Nearestinteger = Doublemath.roundtobiginteger (d, Roundingmode.half_even); BigInteger sidelength = bigintegermath.sqrt (area, CEILING);

Why use Guava Math

• Guava math is fully tested for a variety of unusual overflow situations, as well as a description of overflow semantics and guava documentation, which can cause rapid failure if the overflow check of the operation fails;
• Guava Math's performance has been carefully designed and tuned, although performance inevitably varies based on specific hardware details, but guava math can often be compared to the mathutils of Apache Commons, and there are even significant improvements in some scenarios.
• Guava Math has been designed with readability and proper programming in mind, meaning intmath.log2 (x, CEILING) is clearly defined even in fast reading. and 32-integer.numberofleadingzeros (x–1) is not clear enough for the reader.

Note: Guava math and GWT are exceptionally incompatible because the Java and Java script languages have different arithmetic overflow logic.

Integer arithmetic

Guava Math mainly handles three types of integers: int, long, and BigInteger. These three types of arithmetic tools are called Intmath, Longmath, and Bigintegermath, respectively.

Operations with overflow checking

Guava Math provides several computational methods for overflow checking: When results overflow, these methods will fail quickly rather than ignore overflow

Intmath.checkedadd	Longmath.checkedadd
Intmath.checkedsubtract	Longmath.checkedsubtract
Intmath.checkedmultiply	Longmath.checkedmultiply
Intmath.checkedpow	Longmath.checkedpow

Intmath.checkedadd (Integer.max_value, Integer.max_value); Throws ArithmeticException

Real arithmetic

IntMath, Longmath, and Bigintegermath provide many methods of real-number arithmetic and round the results of the final operation into integers. These methods accept a Java.math.RoundingMode enumeration value as the rounding pattern:

• Down: Rounded in 0 direction (de-tailed method)
• Up: Rounding away from 0 direction
• Floor: Rounding to negative infinity direction
• CEILING: Rounding to positive infinity direction
• Unnecessary: No rounding is required, and if rounded with this mode, it should be thrown directly arithmeticexception
• HALF_UP: Rounds to the nearest integer, where x.5 is rounded away from the 0 direction
• Half_down: Rounds to the nearest integer, where x.5 rounds in 0 direction
• Half_even: Rounds to the nearest integer, where x.5 rounds to adjacent even numbers

These methods are designed to improve the readability of your code, for example, divide (x, 3, CEILING) is clear even when reading quickly. In addition, these methods are implemented internally using the construction of integer approximation recalculation, in addition to floating-point operations when constructing the initial approximation of the sqrt (square root) operation, the whole process of the other methods is integer or bitwise operation, so the performance is better.

Operation	IntMath	Longmath	Bigintegermath
Division	Divide (int, int, roundingmode)	Divide (long, long, Roundingmode)	Divide (BigInteger, BigInteger, Roundingmode)
2 logarithm of the base	log2 (int, roundingmode)	Log2 (Long, Roundingmode)	Log2 (BigInteger, Roundingmode)
10 logarithm of the base	log10 (int, roundingmode)	LOG10 (Long, Roundingmode)	LOG10 (BigInteger, Roundingmode)
Square root	sqrt (int, roundingmode)	sqrt (long, Roundingmode)	sqrt (BigInteger, Roundingmode)

Returns 31622776601683793319988935444327185337195551393252BIGINTEGERMATH.SQRT (BigInteger.TEN.pow (99), Roundingmode.half_even);

Additional Features

Guava also provides a number of useful arithmetic functions

Operation	IntMath	Longmath	Bigintegermath *
Greatest common divisor	GCD (int, int)	GCD (long, long)	BIGINTEGER.GCD (BigInteger)
Take the mold	MoD (int, int)	MoD (long, long)	Biginteger.mod (BigInteger)
Take power	POW (int, int)	POW (long, int)	Biginteger.pow (int)
Whether the power of 2	Ispoweroftwo (int)	Ispoweroftwo (Long)	Ispoweroftwo (BigInteger)
Factorial	factorial (int)	factorial (int)	factorial (int)
Two-item coefficient *	binomial (int, int)	binomial (int, int)	binomial (int, int)

*biginteger greatest common divisor and modulo operations are provided by the JDK

* Factorial and two-key arithmetic results if overflow, return max_value

Floating-point arithmetic

The JDK completely covers the floating-point arithmetic, but guava also provides some useful methods in the Doublemath class.

Ismathematicalinteger (Double)	Determine if the floating-point number is an integer
Roundtoint (double, roundingmode)	rounds to int; throws an exception on an infinite decimal, overflow
Roundtolong (double, roundingmode)	Rounds to long; throws an exception on an infinite decimal, overflow
Roundtobiginteger (double, roundingmode)	Rounds to BigInteger; throws an exception on an infinite decimal
LOG2 (double, roundingmode)	2 floating-point logarithm, and rounded to int, faster than JDK Math.log (double)

Guava 12-mathematical operations