Module java.base
Package java.lang

Class StrictMath


public final class StrictMath extends Object
The class StrictMath contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.

To help ensure portability of Java programs, the definitions of some of the numeric functions in this package require that they produce the same results as certain published algorithms. These algorithms are available from the well-known network library netlib as the package "Freely Distributable Math Library," fdlibm. These algorithms, which are written in the C programming language, are then to be understood to be transliterated into Java and executed with all floating-point and integer operations following the rules of Java arithmetic. The following transformations are used in the transliteration:

  • Extraction and setting of the high and low halves of a 64-bit double in C is expressed using Java platform methods that perform bit-wise conversions from double to long and long to double.
  • Unsigned int values in C are mapped to signed int values in Java with updates to operations to replicate unsigned semantics where the results on the same textual operation would differ. For example, >> shifts on unsigned C values are replaced with >>> shifts on signed Java values. Sized comparisons on unsigned C values (<, <=, >, >=) are replaced with semantically equivalent calls to compareUnsigned.

The Java math library is defined with respect to fdlibm version 5.3. Where fdlibm provides more than one definition for a function (such as acos), use the "IEEE 754 core function" version (residing in a file whose name begins with the letter e). The methods which require fdlibm semantics are sin, cos, tan, asin, acos, atan, exp, log, log10, cbrt, atan2, pow, sinh, cosh, tanh, hypot, expm1, and log1p.

The platform uses signed two's complement integer arithmetic with int and long primitive types. The developer should choose the primitive type to ensure that arithmetic operations consistently produce correct results, which in some cases means the operations will not overflow the range of values of the computation. The best practice is to choose the primitive type and algorithm to avoid overflow. In cases where the size is int or long and overflow errors need to be detected, the methods whose names end with Exact throw an ArithmeticException when the results overflow.

IEEE 754 Recommended Operations

The Math class discusses how the shared quality of implementation criteria for selected Math and StrictMath methods relate to the IEEE 754 recommended operations.
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