``` String s="xxx"; String[] split = s.split("。"); int half=split.length/2; ArrayList<String> pre = new ArrayList<>(); ArrayList<String> post = new ArrayList<>(); for (int i = 0; i < split.length; i++) { if (i<half) pre.add(split[i]); else post.add(split[i]); } for (int i = 0; i < half; i++) { System.out.print(pre.get(i)+"--"); System.out.println(post.get(i)); }