使用分隔符将List<List<String>>连接到单个字符串中

import java.util.List;

public class ListToString {
    public static String convertToString(List<List<String>> list, String innerSeparator, String outerSeparator) {
        StringBuilder sb = new StringBuilder();
        
        for (List<String> innerList : list) {
            StringBuilder innerSb = new StringBuilder();
            
            for (String str : innerList) {
                innerSb.append(str).append(innerSeparator);
            }
            
            // 删除最后一个内层List分隔符
            if (innerSb.length() > 0) {
                innerSb.setLength(innerSb.length() - innerSeparator.length());
            }
            
            sb.append(innerSb).append(outerSeparator);
        }
        
        // 删除最后一个外层List分隔符
        if (sb.length() > 0) {
            sb.setLength(sb.length() - outerSeparator.length());
        }
        
        return sb.toString();
    }
    
    public static void main(String[] args) {
        List<List<String>> list = List.of(
            List.of("A", "B", "C"),
            List.of("D", "E", "F"),
            List.of("G", "H", "I")
        );
        
        String result = convertToString(list, ",", ";");
        System.out.println(result);
    }
}