java 如何在java中使用正则表达式匹配给定字符串的开始或结束
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How to match start or end of given string using regex in java
提问by Galet
I want to match a string which starts or ends with a "test" using regex in java.
我想在java中使用正则表达式匹配一个以“test”开头或结尾的字符串。
Match Start of the string:- String a = "testsample";
匹配字符串的开头：- String a = "testsample";
String pattern = "^test";
// Create a Pattern object
Pattern r = Pattern.compile(pattern);
// Now create matcher object.
Matcher m = r.matcher(a);
Match End of the string:- String a = "sampletest";
匹配字符串的结尾：- String a = "sampletest";
String pattern = "test$";
// Create a Pattern object
Pattern r = Pattern.compile(pattern);
// Now create matcher object.
Matcher m = r.matcher(a);
How can I combine regex for starts or ends with a given string ?
如何将开始或结束的正则表达式与给定的字符串结合使用？
回答by Avinash Raj
Just use regex alternation operator |.
只需使用正则表达式交替运算符|。
String pattern = "^test|test$";
In matchesmethod, it would be,
在matches方法上，它会是，
string.matches("test.*|.*test");
回答by Ajmal Muhammad
use this code
使用此代码
String string = "test";
String pattern = "^" + string+"|"+string+"$";
// Create a Pattern object
Pattern r = Pattern.compile(pattern);
// Now create matcher object.
Matcher m = r.matcher(a);
回答by Wiktor Stribi?ew
Here is how you can build a dynamic regex that you can use both with Matcher#find()and Matcher#matches():
以下是如何构建可以与Matcher#find()和一起使用的动态正则表达式Matcher#matches()：
String a = "testsample";
String word = "test";
String pattern = "(?s)^(" + Pattern.quote(word) + ".*$|.*" + Pattern.quote(word) + ")$";
// Create a Pattern object
Pattern r = Pattern.compile(pattern);
// Now create matcher object.
Matcher m = r.matcher(a);
if (m.find()){
System.out.println("true - found with Matcher");
}
// Now, the same pattern with String#matches:
System.out.println(a.matches(pattern));
See IDEONE demo
The patternwill look like ^(\Qtest\E.*$|.*\Qtest\E)$(see demo) since the wordis searched for as a sequence of literal characters (this is achieved with Pattern.quote). The ^and $that are not necessary for matchesare necessary for find(and they do not prevent matchesfrom matching, either, thus, do not do any harm).
该pattern会像^(\Qtest\E.*$|.*\Qtest\E)$（见演示），因为word中搜索作为文本字符的序列（这是与实现Pattern.quote）。在^和$那些没有必要的matches是必要的find（他们不阻止matches从匹配，要么，因此不会做任何伤害）。
Also, note the (?s)DOTALL inline modifier that makes a .match any character includinga newline.
另外，请注意(?s)DOTALL 内联修饰符，它可以.匹配任何字符，包括换行符。
