使用StringTokenizer解析字符串提取信息时出现异常行为该如何修正

• StringTokenizer的nextToken(String delim)的入参是单字符分隔符集合，不是完整匹配的字符串。你传入"by"时，b和y两个字符都会被识别为分隔符，所以Charlie Montoya末尾的y被切分，导致作者名被截断、date字段错位。
• 读取id时调用nextToken(".")后，解析位置停在.之前，未消费的.会被带入下一次读取的内容开头，导致title前缀多出冗余点号。

方案1：调整StringTokenizer逻辑（兼容原有写法） #

String line = "21. Sponge Cake by Charlie Montoya [2014-10-13]";
StringTokenizer tokenizer = new StringTokenizer(line, " ");
// 提取id
String id = tokenizer.nextToken(".").trim();
// 跳过id后的.和前置空格
tokenizer.nextToken(" ");
// 提取title：读到by标识为止
String title = tokenizer.nextToken("by").trim();
// 跳过by和前置空格
tokenizer.nextToken(" ");
// 提取author：读到日期左括号为止
String author = tokenizer.nextToken("[").trim();
// 提取日期：读到右括号为止
String date = tokenizer.nextToken("]").trim();

// 输出验证
System.out.println("id = \"" + id + "\";");
System.out.println("title = \"" + title + "\";");
System.out.println("author = \"" + author + "\";");
System.out.println("date = \"" + date + "\";");

方案2：正则表达式解析（更稳定，推荐） #

使用正则匹配直接分组提取所有字段，适配性更强，不会出现分隔符误判问题：

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

public class Parser {
    public static void main(String[] args) {
        String line = "21. Sponge Cake by Charlie Montoya [2014-10-13]";
        // 正则分组：1=id 2=title 3=author 4=date
        Pattern pattern = Pattern.compile("(\\d+)\\. (.*?) by (.*?) \\[(.*?)\\]");
        Matcher matcher = pattern.matcher(line);
        if (matcher.find()) {
            String id = matcher.group(1);
            String title = matcher.group(2);
            String author = matcher.group(3);
            String date = matcher.group(4);
            
            System.out.println("id = \"" + id + "\";");
            System.out.println("title = \"" + title + "\";");
            System.out.println("author = \"" + author + "\";");
            System.out.println("date = \"" + date + "\";");
        }
    }
}

以上两种方案输出均符合要求：

id = "21";
title = "Sponge Cake";
author = "Charlie Montoya";
date = "2014-10-13";

内容的提问来源于stack exchange，提问作者NickJ