java list常用方法总结

1.list截取指定部分

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

2.在指定位置更新内容

public ArrayList<String> attrs = new ArrayList<>();//图层属性
attrs.set(position, "string");

3.判断Arraylis中是否有重复内容

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) + "个跟第" + (j + 1) + "个重复，值是：" + temp);
            }
        }
    }
}

4.java中集合（list）与数组（Array）的相互转化

1) 数组转化为集合

 数组可以转化为List,但是除了显示功能以外,其他功能不能使用,因为通过转换得到的list不知到是什么类型的，可以通过集合的构造方法赋值,来使用其他的功能:

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

2) 集合转化为数组

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

5.Hashmap转化成arraylist

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

6.转换成字符串 join

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

8.排序

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