获取数组中的重复元素

public static void main(String[] args) {
    
        String str = "xx@xx.com,aa@aa.com,aa@aa.com,nn@aa.com,xx@aa.com,xx@xx.com"
        String[] arr = str.split(",")
        System.out.println("arr: " + arr);  //arr: [xx@xx.com, aa@aa.com, aa@aa.com, nn@aa.com, xx@aa.com, xx@xx.com]

        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: [xx@xx.com, aa@aa.com]
    }
}