Java优学网String方法讲解：从基础创建到实战应用，轻松掌握字符串处理技巧

String str = "hello"; str = str + " world"; // 这里并不是修改原对象

// 最常见的几种创建方式 String str1 = "直接赋值"; String str2 = new String("使用构造器"); String str3 = new String(charArray); // 字符数组转换 String str4 = String.valueOf(123); // 其他类型转字符串

String str = getPossibleNullString(); int length = str.length(); // 潜在的空指针异常

// 编译器优化后的效果 String message = "Hello " + name + ", welcome to " + city; // 等价于：new StringBuilder().append("Hello ").append(name)...

public class ProductTitleCleaner {

public static String cleanTitle(String rawTitle) {
    if (rawTitle == null || rawTitle.trim().isEmpty()) {
        return "未知商品";
    }
    
    // 去除多余空格，保留单词间单个空格
    String cleaned = rawTitle.trim().replaceAll("\\s+", " ");
    
    // 首字母大写
    cleaned = capitalizeWords(cleaned);
    
    // 移除特殊字符但保留中文和基本标点
    cleaned = cleaned.replaceAll("[^\\u4e00-\\u9fa5a-zA-Z0-9\\s.,!?]", "");
    
    return cleaned;
}

private static String capitalizeWords(String str) {
    String[] words = str.split("\\s");
    StringBuilder result = new StringBuilder();
    for (String word : words) {
        if (!word.isEmpty()) {
            result.append(Character.toUpperCase(word.charAt(0)))
                 .append(word.substring(1).toLowerCase())
                 .append(" ");
        }
    }
    return result.toString().trim();
}

}