InsertAtEnd.java

public void insertAtEnd(int new_data) {
    Node new_node = new Node(new_data);

    if (head == null) {
      head = new Node(new_data);
      return;
    }

    new_node.next = null;

    Node last = head;
    while (last.next != null)
      last = last.next;

    last.next = new_node;
    return;
  }