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String字符串用逗号隔开
在Java中，有两个方法可以用逗号把String分开
一个是
public String[] split(String regex) {
return split(regex, 0);
}另一个是
public String[] split(String regex, int limit) {
/* fastpath if the regex is a
(1)one-char String and this character is not one of the
RegEx's meta characters ".$|()[{^?*+", or
(2)two-char String and the first char is the backslash and
the second is not the ascii digit or ascii letter.
*/
char ch = 0;
if (((regex.value.length == 1 &&
".$|()[{^?*+".indexOf(ch = regex.charAt(0)) == -1) ||
(regex.length() == 2 &&
regex.charAt(0) == '' &&
(((ch = regex.charAt(1))-'0')|('9'-ch)) < 0 &&
((ch-'a')|('z'-ch)) < 0 &&
((ch-'A')|('Z'-ch)) < 0)) &&
(ch < Character.MIN_HIGH_SURROGATE ||
ch > Character.MAX_LOW_SURROGATE))
{
int off = 0;
int next = 0;
boolean limited = limit > 0;
ArrayList<String> list = new ArrayList<>();
while ((next = indexOf(ch, off)) != -1) {
if (!limited || list.size() < limit - 1) {
list.add(substring(off, next));
off = next + 1;
} else { // last one
//assert (list.size() == limit - 1);
list.add(substring(off, value.length));
off = value.length;
break;
}
}
// If no match was found, return this
if (off == 0)
return new String[]{this};
// Add remaining segment
if (!limited || list.size() < limit)
list.add(substring(off, value.length));
// Construct result
int resultSize = list.size();
if (limit == 0) {
while (resultSize > 0 && list.get(resultSize - 1).length() == 0) {
resultSize--;
}
}
String[] result = new String[resultSize];
return list.subList(0, resultSize).toArray(result);
}
return Pattern.compile(regex).split(this, limit);
}1.如果我们的需求是要让分隔符号可以兼容中英文逗号
可以用
split(String regex)
比如下面的例子
2.如果我们的需求是取到第一个逗号前面的字符串
适合用
split(String regex, int limit)
以逗号为分割符拼接字符串的技巧
答：
不用那么多if判断，让人思维混乱，直接到最后使用deleteCharAt方法去除最后一个逗号即可。
实现代码如下所示
StringBuffer sb = new StringBuffer();
for (String str: list) {
sb.append(str).append(",");
}
String keywordStr = sb.deleteCharAt(sb.length() - 1).toString();