Detailed explanation of List collection and its traversal in Java

1. First of all, the List collection inherits from Collection, which is an interface.

① Collection (the collection framework appeared in JDK1.2 version)

② list: It is ordered, and the elements can be repeated, so the collection system has an index.

Often used are the ArrayList and LinkedList classes that implement this interface

③ Arraylist: The underlying data structure uses an array structure,

Features: Query speed is very fast , but additions and deletions are slightly slower. Threads are not synchronized

LinkedList: The bottom layer uses a linked list data structure.

Features: The addition and deletion speed is very fast, and the query is slightly slower.

           Vector: (Appeared in JDK1.0 version) The bottom layer is an array data structure and thread synchronization. Replaced by ArrayList. (No longer used)

2. Two traversal methods for List:

public class Demo {
  public static void main(String[] args) {
    ArrayList<String> list = new ArrayList<String>();
    list.add("A");
    list.add("B");
    list.add("C");
     
    System.out.println("........第一种遍历方式：for遍历......");
    for (Object li : list) {
      System.out.println(li);
    }
     
    System.out.println("........第二种遍历方式：ListIterator迭代遍历......");
    ListIterator<String> it = list.listIterator();
    while (it.hasNext()) {
      Object obj = it.next();
      System.out.println(obj);
    }
  }
}

Rendering:

3. Use LinkList to simulate a stack or queue data structure. That is: Stack: first in, last out; Queue: first in, first out

class Duilie{
  private LinkedList<Object> link;
  Duilie(){
    link = new LinkedList<Object>();
  }
  public void myAdd(Object obj){
    link.addFirst(obj);
   }
  public Object myGet(){
    return link.removeLast();//先进先出---若要改成先进后出，将removelast()改成removeFirst（）
  }
  public boolean isNull(){
    return link.isEmpty();
  }
}
public class Demo2 {
  public static void main(String[] args) {
    Duilie dl = new Duilie();
    dl.myAdd("java01");
    dl.myAdd("java02");
    dl.myAdd("java03");
    dl.myAdd("java04");
    while(!dl.isNull()){
      System.out.println(dl.myGet());
    }
  }
}

Rendering:

The above is first in, first out. If you want to change it to first in, last out, just change it according to what is written in the code.

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