public static void main(String[] args) {
    
        String str = "[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]"
        String[] arr = str.split(",")
        System.out.println("arr: " + arr);  //arr: [[email protected], [email protected], [email protected], [email protected], [email protected], [email protected]]

        Set listAll = new LinkedHashSet<String>()

         // 获取数组重复的元素
        for (int i = 0; i < arr.length; i++) {
            //System.out.println("arr: " + arr[i]);
            int curr = i;
            for (int j = 0; j < arr.length; j++) {
                if (arr[j] == arr[i] && i != j) {
                    //    System.out.println("solution1: " + arr[i])
                    listAll.addAll(arr[i])
                }
            }

        }
        System.out.println("listAll: " + listAll)  //listAll: [[email protected], [email protected]]
    }
}