具有捕获组的RegEx在Java中不起作用

Question

我的字符串的模式类似于以下内容：

• PSHELF - 2 [PSHELF- MF-6RU ]
• 书架- 5 [书架- M6 ]
• 货架- 6 [货架- M15 ]
• 货架- 6 [货架- M15 ]

我想突出显示信息。
为此，我使用以下正则表达式：

(.*SHELF)-(.*)\[.*SHELF-(.*)\]

我用regex101

进行了测试

如果我尝试在 Java

上实现相同的登录

Pattern pattern = Pattern.compile("(.*SHELF)-(.*)\\[.*SHELF-(.*)\\]");
Matcher matcher = pattern.matcher(inputString);
String group1 = matcher.group(1);
String group2 = matcher.group(2);
String group3 = matcher.group(3);

我遇到以下错误：

java.lang.IllegalStateException: No match found

那是为什么？

Answer 1

This post回答您的原始问题。

---

This expression创建捕获组并以多种形式返回所需的输出：

(([A-Z]+)-([0-9]+))\[([A-Z]+)-([A-Z0-9-]+)(\])

，如果需要，您可以进一步简化它。

Java测试

import java.util.regex.Matcher;
import java.util.regex.Pattern;

final String regex = "(([A-Z]+)-([0-9]+))\\[([A-Z]+)-([A-Z0-9-]+)(\\])";
final String string = "PSHELF-2[PSHELF-MF-6RU]\n"
     + "SHELF-5[SHELF-M6]\n"
     + "SHELF-6[SHELF-M15]\n"
     + "SHELF-6[SHELF-M15]";
final String subst = "\\1 \\4";

final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
final Matcher matcher = pattern.matcher(string);

// The substituted value will be contained in the result variable
final String result = matcher.replaceAll(subst);

System.out.println("Substitution result: " + result);

JavaScript演示

const regex = /(([A-Z]+)-([0-9]+))\[([A-Z]+)-([A-Z0-9-]+)(\])/gm;
const str = `PSHELF-2[PSHELF-MF-6RU]
SHELF-5[SHELF-M6]
SHELF-6[SHELF-M15]
SHELF-6[SHELF-M15]`;
const subst = `\nGroup 1: $1\nGroup 2: $2\nGroup3: $3\nGroup 4: $4\nGroup 5: $5`;

// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);

console.log('Substitution result: ', result);

RegEx描述图

此图显示了表达式的工作方式，您可以在此link中可视化其他表达式：

基本性能测试

此JavaScript代码段使用简单的100万次for循环来显示表达式的性能。

const repeat = 1000000;
const start = Date.now();

for (var i = repeat; i >= 0; i--) {
	const string = 'PSHELF-2[PSHELF-MF-6RU]';
	const regex = /(([A-Z]+)-([0-9]+))\[([A-Z]+)-([A-Z0-9-]+)(\])/gm;
	var match = string.replace(regex, "\nGroup #1: $1\nGroup #2: $2 \nGroup #3: $3 \nGroup #4: $4\nGroup #5: $5\n");
}

const end = Date.now() - start;
console.log("YAAAY! \"" + match + "\" is a match  ");
console.log(end / 1000 + " is the runtime of " + repeat + " times benchmark test.  ");