Java中的链表实现

Question

I came across a sample program that adds numbers to linked list

import java.util.LinkedList;

class Node {
    public int data;
    public Node next;
    Node(int d){
        data=d;
    }
    public static void main(String args[]){
        LinkList f1 = new LinkList();
        for(int j=0;j<=10;j++){
        f1.inject(j);
        }
        f1.display();
    }

}
class LinkList {
    Node firstlink;
    LinkList(){
        firstlink=null;
    }
    void inject(int a){
     Node pw=new Node(a);
        pw.next=firstlink;
        firstlink=pw;
    }
    void display(){
       Node pw=firstlink;
        while(pw !=null){
            System.out.println(pw.data);
            pw=pw.next;
        }
    }

}

I have some doubt regarding how it's implemented here . first how does

Node pw=new Node(a);
        pw.next=firstlink;
        firstlink=pw;

adds item to linked list ? and why statement

Node pw=firstlink;

what does it do ?

and how will we delete item from linked list?

Answer 1

Injecting element to LinkedList?

The way it is done is every time inject is called new Node is created with the provided integer value.

Node pw=new Node(a);

This newly create Node instance is made to point to the current Head Node

pw.next=firstlink;

and then then the new instance created is made the new Node.

firstlink=pw;

As you know in LinkedList all we have to do is maintain the Head Node. To iterate we simply call next() till != null . In the sample code firstlink represents the Head Node.