为什么它不打印？ 链表

Question

i have a problem that the method in LinkedList class don't print anything.. and i'm trying hard to know what's the problem i hope someone help

the main class

    public static void main(String[] args) {
        LLnode a = new LLnode(10);
        LLnode b = new LLnode(20);
        LLnode c = new LLnode(50);
        LinkedList List1 = new LinkedList();
      
      List1.printAllNodes();
    }
}

LinkedList class

public class LinkedList {
   
   private LLnode head;
   
  public LLnode gethead() {
        return this.head;
    }
    public void sethead(LLnode LLnode) {
        this.head = LLnode;
    }
   // Constructor
   public LinkedList() {
      head = null;
   }
   // Example Method to check if list is empty
   public boolean isEmpty() {
      return head == null;
   }
   
   public void printAllNodes() {
    LLnode helpPtr = head;
    while (helpPtr != null) {
        System.out.print(helpPtr.getdata() + " ");
        helpPtr = helpPtr.getnext();
   }

why it dosn't print i tried so hard

Answer 1

This is because you never add any nodes to your LinkedList.

Code could be as follows. Beware, nodes will be added at the beginning of list.

Main class:

public static void main(String[] args) {
    LLnode a = new LLnode(10);
    LLnode b = new LLnode(20);
    LLnode c = new LLnode(50);
    LinkedList List1 = new LinkedList();
    List1.add(a).add(b).add(c);
  
  List1.printAllNodes();
}

}

LinkedList class:

public class LinkedList {
   
   private LLnode head;
   
  public LLnode gethead() {
        return this.head;
    }
    public void sethead(LLnode LLnode) {
        this.head = LLnode;
    }
   // Constructor
   public LinkedList() {
      head = null;
   }
   // Example Method to check if list is empty
   public boolean isEmpty() {
      return head == null;
   }
   
   public LinkedList add(LLnode node){
       LLnode oldHead = this.head();
       this.head = node;
       node.setNext(oldHead);
       return this;
   }

   public void printAllNodes() {
    LLnode helpPtr = head;
    while (helpPtr != null) {
        System.out.print(helpPtr.getdata() + " ");
        helpPtr = helpPtr.getnext();
   }
}