通过正则表达式提取 Email 地址的Java代码详解编程语言

import java.util.regex.Matcher; 
import java.util.regex.Pattern; 
import java.io.BufferedReader; 
import java.io.File; 
import java.io.FileReader; 
import java.io.IOException; 
 
public class RegularExpression { 
    public static void main(String[] args) throws IOException { 
 
        // Simple expression to find a valid e-mail address in a file 
        Pattern pattern = Pattern.compile("[A-Z0-9._%+-]+@[A-Z0-9.-]+//.[A-Z]{2,4}"); 
        // Read file, find valid mail addresses and print result 
        File file = new File("test.txt"); 
        BufferedReader in = new BufferedReader(new FileReader(file)); 
        int lines = 0; 
        int matches = 0; 
        for (String line = in.readLine(); line != null; line = in.readLine()) { 
            lines++; 
            Matcher matcher = pattern.matcher(line.toUpperCase()); 
            if (matcher.matches()) {     
                System.out.println(lines + ": '" + line + "'"); 
                matches++; 
            } 
        } 
        // output of summary 
        if (matches == 0) {     
            System.out.println("No matches in " + lines + " lines"); 
        } else { 
            System.out.println("/n" + matches + " matches in " + lines + " lines"); 
        } 
    } 
}