java7新特性-关于数字的下划线分隔符-优快云博客

本文链接：https://blog.youkuaiyun.com/sustbeckham/article/details/6650404

本文介绍Java 7中引入的新特性——在数字中使用下划线以提高代码可读性。详细解释了该特性的使用规则及注意事项，并通过多个示例展示如何在不同类型的数字字面量中正确插入下划线。

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/**
*   author:sustbeckham
*   java7新特性，数字类型上可以加下划线"_", 为了增强可读性。 
*   不适用的地方：
*   1. 在数字的开头
*	2. 在小数点的左边或者右边
*	3. 在Long或者Float型的后缀符F或者L的左边或者右边
*	4. 不能拆散二进制八进制十六进制数字 比如原本的0X被拆成0_X
*
*	总的来说，个人觉得，这个语法的增强...有那么一丝鸡肋的意味。
**/
public class Underscore
{
	public static void main(String args[]){
	    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;
		// 这是一个比较好的增强可读性的例子
		long bank_card = 4367_4298_4082_7152_765L;

		// 但是...
		//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
	}
}