public static void main(String[] args) {
		List<Integer> list = new ArrayList<Integer>();
		list.add(1);
		list.add(2);
		list.add(3);
		list.add(4);
		System.out.println(list);
		int one = 0;
		int two = 0;
		for (int i = 0; i < list.size(); i++) {
			int n = list.get(i);
			if(5 == n){
				if(i-1>=0){
					one = list.get(i-1);
				}
				if(list.size() > i+1){
					two = list.get(i+1);
				}
			}
		}
		System.out.println("上一個："+one);
		System.out.println("下一個："+two);
	}