Java——String.split()函数

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Splits this string around matches of the given regular expression.

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

The string "boo:and:foo", for example, yields the following results with these expressions:

Regex	Result
:	{ "boo", "and", "foo" }
o	{ "b", "", ":and:f" }

Parameters:

regex the delimiting regular expression

Returns:

the array of strings computed by splitting this string around matches of the given regular expression

Throws:

PatternSyntaxException - if the regular expression's syntax is invalid

Since:

1.4

See Also:

java.util.regex.Pattern

@spec

JSR-51

但是要注意以下几点：

(1)如果用“.”作为分隔的话必须是如下写法String.split("\\."),这样才

能正确的分隔开不能用String.split(".");

比如这段代码：

String str="123.456";
String []arrStr=str.split(".");
System.out.println(arrStr.length);

结果为：

而：

String str="123.456";
String []arrStr=str.split("\\.");
System.out.println(arrStr.length);

结果为：

原因是

Splits this string around matches of the given regular expression.要求的是一个正则表达式所以必须满足正则表达式的形式，

因此需要进行转义才行。

下面给出split()函数的源代码供参考：

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);
}

public String[] split(String regex) {
return split(regex, 0);
}