java - 在Java中从double转换为float

Question

如果我正在使用 double，并将其转换为 float，这究竟是如何工作的？该值是否被截断以适合 float ？或者值是否以不同的方式四舍五入？对不起，如果这听起来有点补救，但我试图掌握 float 和 double 转换的概念。

Answer 1

来自 Java Language Specification, section 5.1.3 :

A narrowing primitive conversion from double to float is governed by the IEEE 754 rounding rules (§4.2.4). This conversion can lose precision, but also lose range, resulting in a float zero from a nonzero double and a float infinity from a finite double. A double NaN is converted to a float NaN and a double infinity is converted to the same-signed float infinity.

和section 4.2.4说:

The Java programming language requires that floating-point arithmetic behave as if every floating-point operator rounded its floating-point result to the result precision. Inexact results must be rounded to the representable value nearest to the infinitely precise result; if the two nearest representable values are equally near, the one with its least significant bit zero is chosen. This is the IEEE 754 standard's default rounding mode known as round to nearest.