Java 基本类型占用字节问题 jdk1.8, 以及小数点边界

//基本类型的赋值操作, 超过范围会有检查异常
byte a = 127; // -128~127 有符号 占用 1个字节
byte b = -128;
char c = Character.MAX_VALUE; //最大值等于 \uFFFF=65535
char d = (1 << 2 * Byte.SIZE) - 1; //0~65535, 占用两个字节 无符号
short e = (1 << (2 * Byte.SIZE - 1)) - 1; // -32768~32767 两个字节 有符号 上边界
short f = -(1 << 2 * Byte.SIZE - 1);// 下边界
int g = 0x7FFFFFFF; //-2147483648~2147483647 四个字节 有符号 上边界
int h = Integer.MAX_VALUE; //上边界
int i = 0x80000000; //下边界
long j = 0x7FFFFFFFFFFFFFFFL;//-9223372036854775808~9223372036854775807 八个字节 有符号 上边界
long k = Long.MAX_VALUE;//上边界
long l = 0x8000000000000000L; //下边界
long m = Long.MIN_VALUE;//下边界
float n = 0x1.fffffeP+127f;// 3.4028235e+38f 4个字节 上边界 {@link https://en.wikipedia.org/wiki/IEEE_754}
float o = Float.MAX_VALUE;//
float p = 0x0.000002P-126f;//下边界 1.4e-45f
float q = Float.MIN_VALUE;//
double r = 0x1.fffffffffffffP+1023;//1.7976931348623157e+308 占用8个字节 有符号 上边界
double s = Double.MAX_VALUE;
double t = 0x1.0p-1022; //下边界
double u = Double.MIN_VALUE;
boolean v = true;
boolean w = false;

小数点的边界定义采用了 EEE Standard for Floating-Point Arithmetic (IEEE 754)  标准

https://en.wikipedia.org/wiki/IEEE_754

Name	Common name	Base	Significand bits[b] or digits	Decimal digits	Exponent bits	Decimal E max	Exponent bias[10]	E min	E max	Notes
binary16	Half precision	2	11	3.31	5	4.51	24−1 = 15	−14	+15	not basic
binary32	Single precision	2	24	7.22	8	38.23	27−1 = 127	−126	+127
binary64	Double precision	2	53	15.95	11	307.95	210−1 = 1023	−1022	+1023
binary128	Quadruple precision	2	113	34.02	15	4931.77	214−1 = 16383	−16382	+16383
binary256	Octuple precision	2	237	71.34	19	78913.2	218−1 = 262143	−262142	+262143	not basic
decimal32		10	7	7	7.58	96	101	−95	+96	not basic
decimal64		10	16	16	9.58	384	398	−383	+384
decimal128		10	34	34	13.58	6144	6176	−6143	+6144