List集合，Array数组，String字符串相互转换

//一、Array转String
//方法1：
        //需要引入Apache Commons组件中的个commons-lang.jar包：
      String[] ary = { "1", "2" };
    String str = StringUtils.join(ary, ",");
    System.out.println(str);
//方法2：
         String[] userIds = { "1", "2d", "3dd" };
     StringBuffer userIdsStr = new StringBuffer();
     for (String i : userIds) {
          userIdsStr.append(i).append(",");
     }
     System.out.println(userIdsStr.subString(0, userIdsStr.length() - 1));
 
//方法3：
        String[] userIds = { "1", "2d", "3dd" };
     System.out.println(Arrays.toString(userIds).substring(1, Arrays.toString(userIds).length() - 1).replaceAll(" ", ""));

//二、Array转List
       String[] ss = { "JJ", "KK" };
        List<String> list1 = Arrays.asList(ss);
        List<String> list2 = Arrays.asList("AAA", "BBB");
        System.out.println(list1);
        System.out.println(list2);
 
//三、List转String
       List<String> list = new ArrayList<String>();
        for (int i = 0; i < 5; i++) {
            list.add(i + "");
        }
 
        StringBuilder result = new StringBuilder();
        for (String s : list) {
            result.append(s).append(",");
        }
        System.out.println(result.substring(0, result.length() - 1));
 
//四、List转Array
       List<String> list = new ArrayList<String>();
 
        for (int i = 0; i < 5; i++) {
            list.add(i + "");
        }
 
        String[] str = list.toArray(new String[] {});
              System.out.println(str);
 
//五、String转Array
String str = "1,2,3,4,"; //最后的逗号不用截取 print {"1","2","3","4"}
String[] array = str.split(",");
System.out.println(array);
 
//六、String转List
       String str = "0,1,2,3,4";
        List<String> list = Arrays.asList(str.split(","));
        System.out.println(list);
//七、List转Set
     List<String> list = new ArrayList<String>();
 
      Set<String> set = new HashSet<String>(list.size());
//八、Set转List
    Set<String> set = new HashSet<String>();
     List<String> list = new ArrayList<String>(set.size());