Java字符文字值与getNumericValue（） [英] Java Character literals value with getNumericValue()

问题描述

为什么我会为大小写文字取得相同的结果？例如：

Why do I get the same results for both upper- and lowercase literals? For instance:

char ch1 = 'A';
char ch2 = 'a';
char ch3 = 'Z';
char ch4 = 'z';

print("ch1 -- > " + Integer.toBinaryString(Character.getNumericValue(ch1)));
print("ch2 -- > " + Integer.toBinaryString(Character.getNumericValue(ch2)));
print("ch3 -- > " + Integer.toBinaryString(Character.getNumericValue(ch3)));
print("ch4 -- > " + Integer.toBinaryString(Character.getNumericValue(ch4)));

结果我得到：

ch1 -- > 1010
ch2 -- > 1010
ch3 -- > 100011
ch4 -- > 100011

并没有真正看到'A'和'a'之间的区别。即使我使用UTF形式的字符文字（\\\A代表'A'和\\\a代表'a'），我也得到相同的结果。

And don't really see the difference between 'A' and 'a'. Even if I use character literals in UTF form (\u0041 for 'A' and \u0061 for 'a') I do get the same results.

推荐答案

它的行为与

It's behaving exactly as documented:

字母AZ大写（'\\\A'至'\\\Z'），小写'\\\a'到'\\\z'）和全宽度变量（'\\\Ａ'到'\\\Ｚ'和'\\\ａ'到'\\\ｚ'）形式的数值从10到35 。

The letters A-Z in their uppercase ('\u0041' through '\u005A'), lowercase ('\u0061' through '\u007A'), and full width variant ('\uFF21' through '\uFF3A' and '\uFF41' through '\uFF5A') forms have numeric values from 10 through 35.

基本上这意味着当解析hex（比如说）时， 0xfa == 0xFA

Basically this means that when parsing hex (say), 0xfa == 0xFA, as you'd expect.

我希望在使用像base64这样的东西时，情况非常重要。

I'd only expect case to matter when using something like base64.

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