提取特定字符¶
提取特定字符，例如从123abc123中提取出abc。
正则表达式需要使用小括号。
提取特定符号内的字符¶
例如从[[Rust]]中提取出Rust。前后的中括号当作是标记物。
需要类似\\[\\[(.*?)\\]\\]的正则表达式。中括号需要转义。别忘了最里面的小括号。
调用matcher.find()之后，调用matcher.group()可得到包含两边符号的字符串。
调用matcher.group(1)可得到内部的字符串。
中括号示例1¶
测试代码。注意转义符号的个数。
public static void main(String[] args) {
final String[] regs = {"\\[[(.*?)]\\]", "\\[\\[(.*?)\\]\\]"};
final String[] strs = {"[[Rust]]", "[[[Fisher]]]", "[[abc]", "[abc]]", "[[abc", "[[[[abc]]"};
for (String s : strs) {
for (String r : regs) {
extractTextFrom(r, s);
}
System.out.println();
}
}
private static void extractTextFrom(String reg, String txt) {
if (!txt.matches(reg)) {
System.out.println(txt + " not matches " + reg + "\n");
return;
}
Pattern pattern = Pattern.compile(reg);
Matcher matcher = pattern.matcher(txt);
while (matcher.find()) {
System.out.println(txt + " for " + reg + " group() == " + matcher.group());
System.out.println(txt + " for " + reg + " group(1) == " + matcher.group(1));
}
}
运行结果
[[Rust]] not matches \[[(.*?)]\]
[[Rust]] for \[\[(.*?)\]\] group() == [[Rust]]
[[Rust]] for \[\[(.*?)\]\] group(1) == Rust
[[[Fisher]]] not matches \[[(.*?)]\]
[[[Fisher]]] for \[\[(.*?)\]\] group() == [[[Fisher]]
[[[Fisher]]] for \[\[(.*?)\]\] group(1) == [Fisher
[[abc] not matches \[[(.*?)]\]
[[abc] not matches \[\[(.*?)\]\]
[abc]] not matches \[[(.*?)]\]
[abc]] not matches \[\[(.*?)\]\]
根据规则提取¶
根据规则提取出字符串。需要用小括号把规则包围起来。
提取非字母包围的字母¶
从 [非字母 字母 非字母] 中提取出字母串。使用正则表达式"[^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,}"。
- [a-zA-Z]表示26个字母（包括大小写）
- [^a-zA-Z]表示26个字母之外
- [^a-zA-Z]{0,} 表示0次或不限次数匹配字母；{0,} 可用星号*代替
- ([a-zA-Z]{1,})小括号表示提取至少出现1次的字母；{1,}可用加号+代替
- 正则表达式中只有1个小括号，我们可以调用matcher.group(1)获取提取结果
测试代码
public static void main(String[] args) {
final String[] regs = {
"[^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,}"
};
final String[] textArr = {"!", "!!!", "?!Rust", "Fisher:'", "?!thanks!?", "<<how>>"};
for (String r : regs) {
for (String s : textArr) {
extractTextFrom(r, s);
System.out.println();
}
}
}
private static void extractTextFrom(String reg, String txt) {
if (!txt.matches(reg)) {
System.out.println(txt + " not matches " + reg + "\n");
return;
}
Pattern pattern = Pattern.compile(reg);
Matcher matcher = pattern.matcher(txt);
while (matcher.find()) {
System.out.println(txt + " for " + reg + " group() == " + matcher.group());
for (int i = 0; i <= matcher.groupCount(); i++) {
System.out.println(txt + " for " + reg + " group(" + i + ") == " + matcher.group(i));
}
}
}
运行结果
! not matches [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,}
!!! not matches [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,}
?!Rust for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group() == ?!Rust
?!Rust for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(0) == ?!Rust
?!Rust for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(1) == Rust
Fisher:' for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group() == Fisher:'
Fisher:' for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(0) == Fisher:'
Fisher:' for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(1) == Fisher
?!thanks!? for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group() == ?!thanks!?
?!thanks!? for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(0) == ?!thanks!?
?!thanks!? for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(1) == thanks
<<how>> for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group() == <<how>>
<<how>> for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(0) == <<how>>
<<how>> for [^a-zA-Z]{0,}([a-zA-Z]{1,})[^a-zA-Z]{0,} group(1) == how
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