What are the commonly used regular expression tools in Java function libraries?
Java 函数库提供正则表达式工具用于字符串处理任务,包括:Pattern 类编译正则表达式模式,创建 Matcher 对象。Matcher 类执行匹配,提供 find 方法查找匹配、start 和 end 方法获取匹配范围。replaceAll 方法替换匹配子字符串,split 方法分割字符串。实战案例包括验证电子邮件地址和提取 URL 中的域名。
Java 函数库中的常用正则表达式工具
正则表达式是一种强大的工具,可用于在字符串中搜索、查找并替换模式。Java 函数库提供了许多有用的正则表达式类和方法,可用于各种文本处理任务。
1. Pattern 类
Pattern
类表示正则表达式模式。它提供了编译正则表达式字符串并创建 Matcher
对象的方法。
import java.util.regex.Pattern; Pattern pattern = Pattern.compile("PATTERN_HERE");
2. Matcher 类
Matcher
类执行正则表达式模式与输入字符串之间的匹配。它提供了一些方法来检查匹配是否成功,以及提取匹配的结果。
import java.util.regex.Matcher; Matcher matcher = pattern.matcher("INPUT_STRING_HERE");
3. find() 方法
find()
方法用于查找与正则表达式匹配的输入字符串中的第一个子字符串。如果找到匹配项,它将返回 true
,否则返回 false
。
boolean found = matcher.find();
4. start() 和 end() 方法
start()
和 end()
方法返回匹配项在输入字符串中的起始和结束索引。
int start = matcher.start(); int end = matcher.end();
5. replaceAll() 方法
replaceAll()
方法用于使用指定的替换字符串替换输入字符串中所有与正则表达式匹配的子字符串。
String replacedString = inputString.replaceAll("PATTERN_HERE", "REPLACEMENT_STRING");
6. split() 方法
split()
方法用于将输入字符串拆分为与正则表达式匹配的子字符串。
String[] splitString = inputString.split("PATTERN_HERE");
实战案例
验证电子邮件地址
Pattern pattern = Pattern.compile("^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+$"); Matcher matcher = pattern.matcher("example@example.com"); if (matcher.find()) { System.out.println("Valid email address."); } else { System.out.println("Invalid email address."); }
提取 URL 中的域名
Pattern pattern = Pattern.compile("^(?:http(s)?:\\/\\/)?[\\w\\d\\-\\.]+(\\.[\\w\\d\\-\\.]+)*\\.?$"); Matcher matcher = pattern.matcher("https://www.example.com"); if (matcher.find()) { System.out.println("Domain: " + matcher.group(0)); }
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