如何检查字符串是否仅包含ASCII? [英] How to check if a String contains only ASCII?

问题描述

如果字符是字母，则呼叫Character.isLetter(c)返回true.但是，是否有一种方法可以快速查找String是否仅包含ASCII的基本字符?

The call Character.isLetter(c) returns true if the character is a letter. But is there a way to quickly find if a String only contains the base characters of ASCII?

推荐答案

来自番石榴 19.0起，您可以使用:

From Guava 19.0 onward, you may use:

boolean isAscii = CharMatcher.ascii().matchesAllOf(someString);

这使用此处的ASCII包括所有ASCII字符，包括低于0x20(空格)的不可打印字符，例如制表符，换行/返回以及BEL，其代码为0x07和DEL，代码为0x7F.

Here ASCII includes all ASCII characters including the non-printable characters lower than 0x20 (space) such as tabs, line-feed / return but also BEL with code 0x07 and DEL with code 0x7F.

即使在早期版本的注释中指出了代码点，该代码也会错误地使用字符而不是代码点.幸运的是，创建值U+010000或更大的代码点所需的字符使用两个替代字符，其值在ASCII范围之外.因此，即使对于包含表情符号的字符串，该方法仍然可以成功测试ASCII.

This code incorrectly uses characters rather than code points, even if code points are indicated in the comments of earlier versions. Fortunately, the characters required to create code point with a value of U+010000 or over uses two surrogate characters with a value outside of the ASCII range. So the method still succeeds in testing for ASCII, even for strings containing emoji's.

对于没有ascii()方法的早期Guava版本，您可以编写:

For earlier Guava versions without the ascii() method you may write:

boolean isAscii = CharMatcher.ASCII.matchesAllOf(someString);

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