java list經常使用方法總結

1.list截取指定部分

List sublist = new ArrayList();
sublist = new ArrayList<String>(alist.subList(2, 4));

2.在指定位置更新內容

public ArrayList<String> attrs = new ArrayList<>();//圖層屬性
attrs.set(position, "string");

3.判斷Arraylis中是否有重複內容

public static void main(String[] args)
{
    List<String> list = new ArrayList<String>();
    list.add("aa");
    list.add("bb");
    list.add("cc");
    list.add("dd");
    list.add("bb");
    list.add("ee");
    list.add("dd");
    list.add("ff");
    String temp = "";
    for (int i = 0; i < list.size() - 1; i++)
    {
        temp = list.get(i);
        for (int j = i + 1; j < list.size(); j++)
        {
            if (temp.equals(list.get(j)))
            {
                System.out.println("第" + (i + 1) + "個跟第" + (j + 1) + "個重複，值是：" + temp);
            }
        }
    }
}

4.java中集合（list）與數組（Array）的相互轉化

1) 數組轉化爲集合

數組能夠轉化爲List,可是除了顯示功能之外,其餘功能不能使用,由於經過轉換獲得的list不知到是什麼類型的，能夠經過集合的構造方法賦值,來使用其餘的功能:

String[] names ={"劉備","曹操","諸葛亮"};
List list1 = Arrays.asList(names);
list1 = new ArrayList(list1);

2) 集合轉化爲數組

Object[] ary1 = list3.toArray(new String[list3.size()]);
//System.out.println(Arrays.toString(ary1));

5.Hashmap轉化成arraylist

HashMap<String, Marker> hashMap = iMarkerService.getBaiduMarkerMap();
  ArrayList<Marker> markers = new ArrayList<>(hashMap.values());

6.轉換成字符串 join

List<String> userParms=new ArrayList();
String userSql = String.join(" AND ", userParms);

8.排序

Collections.sort(warnRes, new Comparator<WarnRes>() {//按終保日期排序
    public int compare(WarnRes warnRes0, WarnRes warnRes1) {
        return warnRes1.getZbrq().compareTo(warnRes0.getZbrq());
    }
});