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1: list中添加, 获取, 删除元素.
- public class TestList {
- public staic void main(String[] args) {
- List<String> list = new ArrayList<String>();
-
- //添加元素.
- list.add("Tom");
- list.add("Jam");
- list.add("Alix");
-
- //获取元素.
- String str = list.get(0);
-
- //删除元素.
- list.remove(1);
- list.remove("Alix");
-
- //遍历元素.
- for (String s: list) {
- Systtem.out.peintln(s);
- }
- }
-
- }
2: list中是否包含某一个元素.
- public class TestList {
- public static void main(String[] args) {
- List<String> list = new ArrayList<String>();
- list.add("Tom");
- list.add("Alix");
-
- for (int i = 0; i < list.size(); i++) {
- System.out.println(list.get(i));
- }
-
- //判断某一个元素是否在list中.
- String name = "Tom";
- if (list.contains(name)) {
- System.out.println("Tom in list.");
- } else {
- System.out.println("Tom not in list");
- }
- }
- }
3: list中根据索引改变元素的值.
- public class TestList{
- public static void main(String[] args) {
- List<String> list = new ArrayList<String>();
- String[] name = {"zhangsan", "Lisi", "wanger"};
- for (int i = 0; i < name.length; i++) {
- list.add(name[i]);
- }
-
- //根据索引改变list中某一个值.
- list.set(0, "Tom");
-
- for (int i = 0; i < list.size(); i++) {
- System.out.println(list.get(i));
- }
- }
- }
4: list中根据元素的值查看索引的值.
- public class TestListIndexOf{
- piblic static void main(String[] args) {
- List<Integer> num = new ArrayList<Integer>();
-
- num.add(1);
- num.add(2);
- num.add(3);
- num.add(2);
-
- //返回元素值等于2的索引.
- System.out.println(num.indexOf(2));
- //返回元素值等于2的最后的索引.
- System.out.println(num.lastIndexOf(2));
- }
- }
5: 根据元素索引位置进行的判断.
- public class TestList{
- public static void main(String[] args) {
- List<Integer> num = new ArrayList<Integer>();
-
- num.add(1);
- num.add(2);
- num.add(3);
- num.add(2);
-
- if (num.indexOf(3) == 2) {
- System.out.println("元素3在这个位置.");
- }
- if (num.lastIndexOf(2) == 3) {
- System.out.println("最后的元素2在这个位置.");
- }
- }
- }
6: 利用list中索引位置重新生成一个新的list(截取集合).
- public class TestList{
- public static void main(String[] args) {
- List<Integer> num = new ArrayList<Integer>();
- num.add(2);
- num.add(3);
- num.add(6);
- num.add(7);
-
- for (Integer i: num) {
- System.out.println(i);
- }
-
- //利用subList()截取, 然后给num.
- num = num.subList(1, 4);
- for (int i = 0; i < num.size(); i++) {
- System.out.println(num.get(i));
- }
- }
- }
7: 判断list是否为空.
- public class TestList{
- public static void main(String[] args) {
- List<String> arrayList = new ArrayList<>();
-
- arrayList.add("Tom");
-
- //判断list是否为空.
- if (arrayList.isEmpty()) {
- System.out.println("空的.");
- } else {
- System.out.println("不为空.");
- }
- }
- }
8:返回iterator集合对象.
- public class TestList{
- public static void main(String[] args) {
- List<String> arrayList = new ArrayList<>();
- arrayList.add("Tom");
- arrayList.add("Alix");
-
- //转化成iterator对象.
- Iterator it = arrayList.iterator();
- while(it.hasNext) {
- Object obj = it.next();
- System.out.println(obj);
- }
- }
- }
9: 将集合转为string.
- String str = "";
- str = list.toString();
- System.out.println(str);
10: 将集合转为数组.
- String[] str = list.toArray();
- for (String s: str) {
- System.out.println(str);
- }
11: 去重复.
- List<String> lst1=new ArrayList<>();
- lst1.add("aa");
- lst1.add("dd");
- lst1.add("ss");
- lst1.add("aa");
- lst1.add("ss");
-
- //第一种方法通过循环做, 根据remove方法去重复.
- for (int i = 0; i <lst1.size()-1; i++) {
- for (int j = lst1.size()-1; j >i; j--) {
- if (lst1.get(j).equals(lst1.get(i))) {
- lst1.remove(j);
- }
- }
- }
- System.out.println(lst1);
-
- //第二种方法通过frequency方法.
- List<String> lst2=new ArrayList<>();
- for (String s:lst1) {
- if (Collections.frequency(lst2, s)<1) {
- lst2.add(s);
- }
- }
- System.out.println(lst2);
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