Java实现loadDocument方法提取link=后合法标识符的问题求助

Looking at your code, there are a couple of key issues preventing it from correctly extracting and validating the identifiers after "link=":

1. Incorrect line matching: Your current condition checks if the line matches link="+name", which compares the line to a string combining "link=" with the name parameter (not the identifier from the line itself). This is backwards—you need to extract the identifier from the line, not compare it to the method's input.
2. Broken validation regex: The correctLink method uses an invalid regex pattern that doesn't properly validate valid identifiers.

Here's the corrected code that addresses these issues and meets your requirements:

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

public class DocumentLoader {
    public static void loadDocument(String name, Scanner scan) {
        // Case-insensitive pattern to match lines starting with "link=" and capture the identifier
        Pattern linkPattern = Pattern.compile("^link=(.*)$", Pattern.CASE_INSENSITIVE);
        
        while (scan.hasNextLine()) {
            String line = scan.nextLine();
            
            // Stop processing when we hit the "eod" line
            if (line.equals("eod")) {
                return;
            }
            
            // Check if the line matches the link pattern
            Matcher matcher = linkPattern.matcher(line);
            if (matcher.find()) {
                String identifier = matcher.group(1);
                // Validate the identifier and print if valid
                if (correctLink(identifier)) {
                    System.out.println(identifier.toLowerCase());
                }
            }
        }
    }

    // Validates if the input is a legal identifier: starts with letter, followed by letters/digits/underscores
    public static boolean correctLink(String link) {
        return link.matches("^[a-zA-Z][a-zA-Z0-9_]*$");
    }

    // Example main method for testing
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        loadDocument("test", scanner);
        scanner.close();
    }
}

Key Changes Explained: #

• Case-insensitive link matching: The Pattern.CASE_INSENSITIVE flag ensures lines like LINK=MyID, Link=abc123_, and link=XYZ are all detected correctly.
• Identifier extraction: The regex ^link=(.*)$ captures everything after "link=" into a group, which we retrieve with matcher.group(1) to get the raw identifier.
• Proper validation regex: The correctLink method now uses ^[a-zA-Z][a-zA-Z0-9_]*$, which enforces:
  • The first character must be a letter (upper or lowercase)
  • Subsequent characters can be letters, digits, or underscores (any number, including zero)
• Simplified flow: The loop processes each line, checks for the "eod" stop condition first, then handles link extraction and validation.

Example Test Cases: #

• Input line: link=abc → Output: abc
• Input line: LINK=AbC_123 → Output: abc_123
• Input line: link=123Invalid → No output (starts with digit)
• Input line: link=_BadStart → No output (starts with underscore)
• Input line: eod → Stops processing

内容的提问来源于stack exchange，提问作者nme