Java List collection method and code analysis of traversal process

Collection element frame

public class ListDemo02 {
  public static void main(String[] args) {
    //创建集合对象
    List<String> list = new ArrayList<String>();

    //添加元素
    list.add("hello");
    list.add("world");
    list.add("java");

    //输出集合对象
    System.out.println(list); //[hello, world, java]
  }
}

Method running example

//void add(int index, E element) : 在此集合中的指定位置插入指定的元素
    list.add(1,"javaee"); //[hello, javaee, world, java]
    list.add(11,"j2ee");  //IndexOutOfBoundsException


//E remove(int index)：删除指定索引处的元素，返回被删除的元素
    System.out.println(list.remove(1));
    /*
        world
        [hello, java]
     */


//E set(int index,E element)：修改指定索引处的元素，返回被修改的元素
    System.out.println(list.set(1,"javaee"));
    /*
        world
        [hello, javaee, java]
     */


//E get(int index)：返回指定索引处的元素
    System.out.println(list.get(1));
    /*
        world
        [hello, world, java]
     */

//用for循环改进遍历
    for (int i = 0; i<list.size();i++){
      String s = list.get(i);
      System.out.println(s);
    }
    /*
      hello
      world
      java
      [hello, world, java]
     */

The List collection is an indexed collection, and cross-border issues should be considered.

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