List type to string type

Raise questions ：

When deleting videos in batches , With List In the form of multiple videos id When it came in ,
This method request.setVideoIds(id); Parameters in can accept multiple ：request.setVideoIds(id1,id2,id3,…);
So here comes the question , incoming List The parameters are like this ：[id1,id2,id3] , How to handle List Turn into id1,id2,id3 In the form of

Method 1 ： Use StringUtils.join（） Method

1、 Ideas ：
according to import org.apache.commons.lang3.StringUtils; Under this bag StringUtils.join() Method , Not traditional spring Medium

2、 Code display

public static void main(String[] args) {
    
        List<String> list = new ArrayList<>();
        list.add("11");
        list.add("22");
        list.add("33");
        String join = StringUtils.join(list.toArray(), ",");
        System.out.println(join);
    }

result ：

11,22,33

Learn programming ideas alive

3、 Source code analysis

You can't just use StringUtils.join() Method , And understand the principle , that ctrl+ left-click （ Click on join Method ） Look at the method source code ：

public static String join(Object[] array, String separator) {
    
        return array == null ? null : join((Object[])array, separator, 0, array.length);
    }

public static String join(Object[] array, String separator, int startIndex, int endIndex) {
    
        if (array == null) {
    
            return null;
        } else {
    
            if (separator == null) {
    
                separator = "";
            }

            int noOfItems = endIndex - startIndex;
            if (noOfItems <= 0) {
    
                return "";
            } else {
    
                StringBuilder buf = newStringBuilder(noOfItems);
                if (array[startIndex] != null) {
    
                    buf.append(array[startIndex]);
                }

                for(int i = startIndex + 1; i < endIndex; ++i) {
    
                    buf.append(separator);
                    if (array[i] != null) {
    
                        buf.append(array[i]);
                    }
                }

                return buf.toString();
            }
        }
    }    

Specific description of source code
1、join() Method parameters are two , One is an array , One is