这些特殊字符在 Java 中是什么意思？
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What do these special characters mean in Java?
提问by JourneyMan
I was looking at some of the jdk code. I found these characters. Could someone explain to me what do these mean.
我在看一些 jdk 代码。我找到了这些字符。有人可以向我解释这些是什么意思。
public static String quote(String s) {
int slashEIndex = s.indexOf("\E"); // What does this mean. Is this a special char in java. if so what does this do.
if (slashEIndex == -1)
return "\Q" + s + "\E";
StringBuilder sb = new StringBuilder(s.length() * 2);
sb.append("\Q");
slashEIndex = 0;
int current = 0;
while ((slashEIndex = s.indexOf("\E", current)) != -1) {
sb.append(s.substring(current, slashEIndex));
current = slashEIndex + 2;
sb.append("\E\\E\Q");
}
sb.append(s.substring(current, s.length()));
sb.append("\E");
return sb.toString();
}
From the above code example I was able to figure out what's happening as in the method finds the occurrences of \ and converts them to \E and \Q. Could someone explain why that's the case.
从上面的代码示例中，我能够弄清楚发生了什么，因为在方法中找到了 \ 的出现并将它们转换为 \E 和 \Q。有人可以解释为什么会这样。
For more context on this method, I was looking into the Pattern.quote() method from jdk 1.6
有关此方法的更多上下文，我正在查看 jdk 1.6 中的 Pattern.quote() 方法
采纳答案by Kumar Vivek Mitra
\Qand \Eis exactly what Pattern.quote()does, that is to Returns a literal pattern String for the specified String.
\Q并且\E正是这样Pattern.quote()做的，即返回指定字符串的文字模式字符串。
For more details see this link:
有关更多详细信息，请参阅此链接：
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html
回答by dasblinkenlight
Java regex engine blocks special interpretation of all meta-characters between \Qand \E. For example, [name]matches a single character ('n', 'a', 'm', or 'e'), while \Q[name]\Ematches six characters - '[', 'n', 'a', 'm', 'e', and ']'. See the Special Characterssection of the regex tutorialfor more detail.
Java的正则表达式引擎块之间的所有元字符特殊的解释\Q和\E。例如，[name]与单个字符匹配（'n'，'a'，'m'，或'e'），而\Q[name]\E火柴六个字符- ，'['，'n'，'a'，'m'，'e'和']'。有关更多详细信息，请参阅正则表达式教程的特殊字符部分。
The method makes a regular expression from a string that is presumably provided externally (e.g. entered by a user). Since the string may contain meta-characters, the method encloses the entire string in \Qand \E. If the string already contains a \E, the method inserts the end of the quote, a match of \E, and a beginning of a new quote for each \Ethat it finds..
该方法根据大概是外部提供的（例如，由用户输入的）字符串生成正则表达式。由于字符串可能包含元字符，因此该方法将整个字符串包含在\Q和 中\E。如果字符串已经包含 a \E，则该方法\E为\E它找到的每个插入引号的结尾、一个匹配项和一个新引号的开头。
回答by Louis Wasserman
Well, \Qand \Ehave a special meaning in Java regular expressions...
好了，\Q并\E在Java中的特殊含义正则表达式...
Most of this method is just working on the tricky edge case of quoting the quote markers \Qand \Ethemselves.
大多数这种方法只是在引用引号\Q和\E它们本身的棘手的边缘情况下工作。
