java 在大写字母后插入空格
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Insert Space After Capital letter
提问by Emil
How to covert "HelloWorld"to "Hello World".The splitting has to take place based on The Upper-Case letters ,but should exclude the first letter.
如何转换"HelloWorld"为"Hello World". 拆分必须基于大写字母进行，但应排除第一个字母。
P.S:I'm aware of using String.split and then combining.Just wanted to know if there is a better way.
PS：我知道使用 String.split 然后组合。只是想知道是否有更好的方法。
回答by Joachim Sauer
String output = input.replaceAll("(\p{Ll})(\p{Lu})"," ");
This regex searches for a lowercase letter follwed by an uppercase letter and replaces them with the former, a space and the latter (effectively separating them with a space). It puts each of them in a capturing group ()in order to be able to re-use the values in the replacement string via back references ($1and $2).
此正则表达式搜索后跟大写字母的小写字母，并将它们替换为前者、空格和后者（有效地用空格分隔它们）。它将它们中的每个放在一个捕获组()中，以便能够通过反向引用（$1和$2）重新使用替换字符串中的值。
To find upper- and lowercase letters it uses \p{Ll}and \p{Lu}(instead of [a-z]and [A-Z]), because it handles allupper- and lowercase letters in the Unicode standard and not just the ones in the ASCII range (this nice explanation of Unicode in regexesmostly applies to Java as well).
要查找它使用的大写和小写字母\p{Ll}和\p{Lu}（而不是[a-z]和[A-Z]），因为它处理Unicode 标准中的所有大写和小写字母，而不仅仅是 ASCII 范围内的字母（正则表达式中对 Unicode 的这个很好的解释主要适用于 Java同样）。
回答by Andreas Dolk
Betteris subjective. This takes some more lines of code:
更好是主观的。这需要更多的代码行：
public static String deCamelCasealize(String camelCasedString) {
if (camelCasedString == null || camelCasedString.isEmpty())
return camelCasedString;
StringBuilder result = new StringBuilder();
result.append(camelCasedString.charAt(0));
for (int i = 1; i < camelCasedString.length(); i++) {
if (Character.isUpperCase(camelCasedString.charAt(i)))
result.append(" ");
result.append(camelCasedString.charAt(i));
}
return result.toString();
}
Hide this ugly implementation in a utility class and use it as an API (looks OK from the user perspective ;) )
将这个丑陋的实现隐藏在一个实用程序类中并将其用作 API（从用户的角度来看似乎没问题；））
回答by Nishant
String s = "HelloWorldNishant";
StringBuilder out = new StringBuilder(s);
Pattern p = Pattern.compile("[A-Z]");
Matcher m = p.matcher(s);
int extraFeed = 0;
while(m.find()){
if(m.start()!=0){
out = out.insert(m.start()+extraFeed, " ");
extraFeed++;
}
}
System.out.println(out);
prints
印刷
Hello World Nishant
你好世界尼桑特
回答by Michael Berry
If you don't want to use regular expressions you could loop through the characters in the string, adding them to a stringbuilder (and adding a space to the string builder if you come across a capital letter that's not the first):
如果您不想使用正则表达式，您可以遍历字符串中的字符，将它们添加到字符串构建器（如果遇到不是第一个大写字母，则向字符串构建器添加一个空格）：
String s = "HelloWorld";
StringBuilder result = new StringBuilder();
for(int i=0 ; i<s.length() ; i++) {
char c = s.charAt(i);
if(i!=0&&Character.isUpperCase(c)) {
result.append(' ');
}
result.append(c);
}
回答by vz0
Pseudocode:
伪代码：
String source = ...;
String result = "";
// FIXME: check for enf-of-source
for each letter in source {
while current letter not uppercase {
push the letter to result;
advance one letter;
}
if not the first letter {
push space to result;
}
push the letter to result;
}
