Java 中使用下划线分隔超大数字(干货)

Java 中下划线分隔数字

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Java 7 以后，数字文字中数字之间的任意位置都可以出现任何数量的下划线字符（_）,通过下划线(_)你可以把数字按组进行分开。从而可以可以提高代码的可读性。

下面的例子介绍如何使用 _ 作为数字之间的分隔符

long creditCardNumber = 1234_5678_9012_3456L;
long socialSecurityNumber = 999_99_9999L;
float pi = 	3.14_15F;
long hexBytes = 0xFF_EC_DE_5E;
long hexWords = 0xCAFE_BABE;
long maxLong = 0x7fff_ffff_ffff_ffffL;
byte nybbles = 0b0010_0101;
long bytes = 0b11010010_01101001_10010100_10010010;

注意: 你只能在数字之间添加下划线，不能在下面位置添加下划线。

• 在数字的开头或者结尾
• 与浮点文字中的小数点相邻
• 后缀 F 或 L 之前
• 在需要一串数字的位置

float pi1 = 3_.1415F;      // Invalid; cannot put underscores adjacent to a decimal point
float pi2 = 3._1415F;      // Invalid; cannot put underscores adjacent to a decimal point
long socialSecurityNumber1
  = 999_99_9999_L;         // Invalid; cannot put underscores prior to an L suffix

int x1 = _52;              // This is an identifier, not a numeric literal
int x2 = 5_2;              // OK (decimal literal)
int x3 = 52_;              // Invalid; cannot put underscores at the end of a literal
int x4 = 5_______2;        // OK (decimal literal)

int x5 = 0_x52;            // Invalid; cannot put underscores in the 0x radix prefix
int x6 = 0x_52;            // Invalid; cannot put underscores at the beginning of a number
int x7 = 0x5_2;            // OK (hexadecimal literal)
int x8 = 0x52_;            // Invalid; cannot put underscores at the end of a number

int x9 = 0_52;             // OK (octal literal)
int x10 = 05_2;            // OK (octal literal)
int x11 = 052_;            // Invalid; cannot put underscores at the end of a number

reference

https://docs.oracle.com/javase/7/docs/technotes/guides/language/underscores-literals.html