Java8中将list转换为用逗号隔开的字符串的几种方法

1.使用谷歌的Joiner转换

 public static <T> String parseListToStr(List<T> list){
       String result = Joiner.on(",").join(list);
       return result;
 }

2.使用lambda表达式遍历集合

public static <T> String parseListToStr2(List<T> list){
     StringBuffer sb = new StringBuffer();
     list.stream().forEach(str->{
         sb.append(str).append(",");
     });
     sb.deleteCharAt(sb.length()-1);
     return sb.toString();
}

3.直接使用stream流实现

public static <T> String parseListToStr3(List<T> list){
     String result = list.stream().map(String::valueOf).collect(Collectors.joining(","));
     return result;
}

4.使用for循环遍历集合

   public static <T> String parseListToStr(List<T> list){
        StringBuffer sb = new StringBuffer();
        if(listIsNotNull(list)) {
            for(int i=0;i<=list.size()-1;i++){
                if(i<list.size()-1){
                    sb.append(list.get(i) + ",");
                }else {
                    sb.append(list.get(i));
                }
            }
        }
        return sb.toString();
    }

注意：在转换集合前应该都统一做判空处理